Gnome BODY (important!)

This is absurd.  Gandalf970 asked a very straight-forward question with a very straight-forward answer and nobody's managed to even touch on it. 
 
@Gandalf970 Reference FREDp296, FREDp297, 6E1p381
 
All that's needed to disrupt casting is to land an attack that's not totally negated by defenses.  A single point of STUN or other such effect is enough to cancel the entire spell. 
The procedure thus becomes holding one's action until the caster casts, winning the DEX vs DEX roll to act first when the caster casts, hitting, and dealing any damage.  This negates the spell, with nothing the caster can do at this point. 
 
6E's Fantasy Hero contains text on page 165 that indicates Gestures and Incantations begin at the start of the Segment, and thus holding until the caster's DEX and the DEX vs DEX roll are unnecessary, making the process even easier.  Just go first on that Segment and hit them. 

Having a high DEX does not mean that you go first.  Having a high DEX means you get to choose when you go.  The biggest mistake most people make with high DEX characters is always going first.  Knowing when to go first and when to allow someone else to go first is what makes a character effective.

P. 387:
 

The point being, slapping on an OIAID gives you a lot of points for a very narrow window, in many cases.  (Pretty easy to put 100-150 points as OIAID, giving you an extra 20-30 to use.)  The key may be, how often does the GM expect to have this window?  
 
Look at the other options.
--Perceivable (inobvious to obvious), typically for defenses.  The fact that it's obvious means your hero ID is blatant, so it's full-time.
--Costs END only to activate.  This one's sweet in many ways...but on the 0 END defenses, they go from Persistent to Constant.  They *stop* if you're stunned or KOd.  
--Concentration 1/2 DCV.  Also has the "can't dodge" aspect, and applies all the way through to his next phase.  (I'm talking about the simple form, with a constant or persistent power.)
--Linked.  Who needs a 1/4 limit when you can get 1/2?  Define the baseline power that creates the conversion from normal to hero form (stun-only Damage Negation anyone?) and hang a ton of Links onto it.  Yes, this is seriously rude.
 
Limitations are meant to cause you problems sometimes.  With OIAID, those problems can't happen most of the time...so when that window's there, it kinda has to be a nasty one.
 

I’m going to disagree here with yah Duke. Yes the game has optional rules and it has house rules (what game doesn’t?). However unless those are stated in the question, the assumption is that we’re looking at RAW. 

So I have built myself a Fantasy Hero character and, with permission from the GM, have an instinctive magician, small VPP that allows me to hurry spells, dispense with gestures, with concentration or any other element as desired.
 
What would Gandalph's character do to interrupt my spellcasting?  Anything guaranteed to work RAW? 
 
All Duke has said is that it might be different in every game and there may be some games in which you cannot interrupt spellcasting.
 
Doc

Gnome BODY I really appreciate this.  I understand there is a lot of what rules would you use answers.  I should reword my questions in the future.  Thanks Ninja-Bear!

This is absurd.  Gandalf970 asked a very straight-forward question with a very straight-forward answer and nobody's managed to even touch on it. 
 
@Gandalf970 Reference FREDp296, FREDp297, 6E1p381
 
All that's needed to disrupt casting is to land an attack that's not totally negated by defenses.  A single point of STUN or other such effect is enough to cancel the entire spell. 
The procedure thus becomes holding one's action until the caster casts, winning the DEX vs DEX roll to act first when the caster casts, hitting, and dealing any damage.  This negates the spell, with nothing the caster can do at this point. 
 
6E's Fantasy Hero contains text on page 165 that indicates Gestures and Incantations begin at the start of the Segment, and thus holding until the caster's DEX and the DEX vs DEX roll are unnecessary, making the process even easier.  Just go first on that Segment and hit them. 

HERO Designer does not have rules in a manner that's accessible to the user.  It enforces character creation rules, but doesn't explain them nor does it have any other rules for user reference.  You will need to purchase the rules separately. 

HERO Designer does not have rules in a manner that's accessible to the user.  It enforces character creation rules, but doesn't explain them nor does it have any other rules for user reference.  You will need to purchase the rules separately. 

I have a friend who I could make swear off d6-1 just by making him roll the d6-1 in a different color and pointing out "That's a zero" every time the die came up '1'.  The half-point average difference is "who cares" for many people while the possibility of it not contributing can be a big psychological deal. 
 
The player might also have a good reason to want low results to be less likely. 

Hunted:  The Writers 8- (Mo Pow; Infinite Non-Combat Influence; Ruin Relationships)

Hunted:  The Writers 8- (Mo Pow; Infinite Non-Combat Influence; Ruin Relationships)

It doesn't matter if you can Abort to the action when you Abort, you can't Abort at all if you've already taken an Attack Action or otherwise used all your Half-Phase Actions this Segment. 
And most things you'd Abort to are Attack Actions.  Dodge, Block, et al are Attack Actions despite not being "attacks". 

In my experience, the process goes something like this: 
Two weeks before session 1: Tell the players that hey, we're shifting GMs for a bit and it was a major story arc we just finished, switch PCs if you want but get me the sheet by [one week before session 1]. 
One week before session 1: I have one PC's sheet.  Ask the players for their sheets ASAP.  Plan anyways, hope to get sheets soon. 
Week leading up to session 1: Complete silence from the players. 
Session 1: All but one player sends me their sheet day-of, generally no more than two hours before game starts.  Plans are already finalized.  Half the PCs have obvious issues that require immediate attention to fix, so there's no time to work the game around the PCs.  The last player seems utterly determined to not hand over their character sheet, for reasons beyond anyone's knowledge. 
After session 1: Too angry at players refusing to provide sheets to give a flying fornication about working them in. 

In my experience, the process goes something like this: 
Two weeks before session 1: Tell the players that hey, we're shifting GMs for a bit and it was a major story arc we just finished, switch PCs if you want but get me the sheet by [one week before session 1]. 
One week before session 1: I have one PC's sheet.  Ask the players for their sheets ASAP.  Plan anyways, hope to get sheets soon. 
Week leading up to session 1: Complete silence from the players. 
Session 1: All but one player sends me their sheet day-of, generally no more than two hours before game starts.  Plans are already finalized.  Half the PCs have obvious issues that require immediate attention to fix, so there's no time to work the game around the PCs.  The last player seems utterly determined to not hand over their character sheet, for reasons beyond anyone's knowledge. 
After session 1: Too angry at players refusing to provide sheets to give a flying fornication about working them in. 

In my experience, the process goes something like this: 
Two weeks before session 1: Tell the players that hey, we're shifting GMs for a bit and it was a major story arc we just finished, switch PCs if you want but get me the sheet by [one week before session 1]. 
One week before session 1: I have one PC's sheet.  Ask the players for their sheets ASAP.  Plan anyways, hope to get sheets soon. 
Week leading up to session 1: Complete silence from the players. 
Session 1: All but one player sends me their sheet day-of, generally no more than two hours before game starts.  Plans are already finalized.  Half the PCs have obvious issues that require immediate attention to fix, so there's no time to work the game around the PCs.  The last player seems utterly determined to not hand over their character sheet, for reasons beyond anyone's knowledge. 
After session 1: Too angry at players refusing to provide sheets to give a flying fornication about working them in. 

VPPs must have a tightly defined SFX.  No vaguely defined "cosmic power VPP (does anything)" or "magic VPP (does anything)". 
You, the player, cannot have the Extra Time Limitation.  When your Phase comes up, you either have the thing you want to VPP fully built or you're not VPPing that thing right now. 
 
These were in response to the guy who took a Cosmic  "magic" VPP as his character's only mode of combat and would take three minutes just to figure out that Fireball is RKA 2d6 AoE.  It was horrible. 

1) handouts - I have found and created some handouts designed to be short and give high level BUT important player info.
2) pregenerated characters - if at convention use these, you will be familiar with them, make sure they have common powers and complications to illustrate game elements
3) danger room - IMHO a good way to show off powers/complications in Champions
4) hero designer software for the the GM - it easily makes characters and save you a LOT of time
5) explain 3d6 - explain the bell shaped curve and why you want/when to  roll low and low high  
6) show quick and easy way to count body - group the dice by 1's; 6's, and all others. Then 1 and 6 cancel out, any excess either way adjust the body amount = normal damage dice.
7) show special effects - complication -> double damage to heat; great way to show a blast is blast; BUT not always depends on SFX.
8) show players it is easy for them, harder for GM - Show them that playing [by actually playing] is easy; the GM must know a lot more than players. The point is once have a GM who has experience, the players need to know a lot less.
 
Again, if you want join my game on Saturday please do so.

In my experience, the process goes something like this: 
Two weeks before session 1: Tell the players that hey, we're shifting GMs for a bit and it was a major story arc we just finished, switch PCs if you want but get me the sheet by [one week before session 1]. 
One week before session 1: I have one PC's sheet.  Ask the players for their sheets ASAP.  Plan anyways, hope to get sheets soon. 
Week leading up to session 1: Complete silence from the players. 
Session 1: All but one player sends me their sheet day-of, generally no more than two hours before game starts.  Plans are already finalized.  Half the PCs have obvious issues that require immediate attention to fix, so there's no time to work the game around the PCs.  The last player seems utterly determined to not hand over their character sheet, for reasons beyond anyone's knowledge. 
After session 1: Too angry at players refusing to provide sheets to give a flying fornication about working them in. 

In my experience, the process goes something like this: 
Two weeks before session 1: Tell the players that hey, we're shifting GMs for a bit and it was a major story arc we just finished, switch PCs if you want but get me the sheet by [one week before session 1]. 
One week before session 1: I have one PC's sheet.  Ask the players for their sheets ASAP.  Plan anyways, hope to get sheets soon. 
Week leading up to session 1: Complete silence from the players. 
Session 1: All but one player sends me their sheet day-of, generally no more than two hours before game starts.  Plans are already finalized.  Half the PCs have obvious issues that require immediate attention to fix, so there's no time to work the game around the PCs.  The last player seems utterly determined to not hand over their character sheet, for reasons beyond anyone's knowledge. 
After session 1: Too angry at players refusing to provide sheets to give a flying fornication about working them in. 

In my experience, the process goes something like this: 
Two weeks before session 1: Tell the players that hey, we're shifting GMs for a bit and it was a major story arc we just finished, switch PCs if you want but get me the sheet by [one week before session 1]. 
One week before session 1: I have one PC's sheet.  Ask the players for their sheets ASAP.  Plan anyways, hope to get sheets soon. 
Week leading up to session 1: Complete silence from the players. 
Session 1: All but one player sends me their sheet day-of, generally no more than two hours before game starts.  Plans are already finalized.  Half the PCs have obvious issues that require immediate attention to fix, so there's no time to work the game around the PCs.  The last player seems utterly determined to not hand over their character sheet, for reasons beyond anyone's knowledge. 
After session 1: Too angry at players refusing to provide sheets to give a flying fornication about working them in. 

In my experience, the process goes something like this: 
Two weeks before session 1: Tell the players that hey, we're shifting GMs for a bit and it was a major story arc we just finished, switch PCs if you want but get me the sheet by [one week before session 1]. 
One week before session 1: I have one PC's sheet.  Ask the players for their sheets ASAP.  Plan anyways, hope to get sheets soon. 
Week leading up to session 1: Complete silence from the players. 
Session 1: All but one player sends me their sheet day-of, generally no more than two hours before game starts.  Plans are already finalized.  Half the PCs have obvious issues that require immediate attention to fix, so there's no time to work the game around the PCs.  The last player seems utterly determined to not hand over their character sheet, for reasons beyond anyone's knowledge. 
After session 1: Too angry at players refusing to provide sheets to give a flying fornication about working them in. 

Maybe this is true in the case of your players, but it's not a universality.  Many players take Limitations for other reasons.  The two big reasons I see at my table are "This Limitation is necessary to simulate the effects the Power should have.  I can't not take it without changing the concept." and "I need points and am willing to deal with this Limitation.". 

Of course it would be a Limitation.  Let's just go down the list of things it does to aid the enemy. 
- The enemy knows it's there.  Foes likely to run into the DR are going to know it, as will foes with attacks likely to bypass it.  Anyone with a relevant Adjustment Power is going to know they've got a target. 
- The enemy knows the SFX.  For example, nobody's going to use a NND: Forcefield attack on somebody with DR defined as a visible forcefield.  It wouldn't do anything and they know it!  But they might have wasted a shot if the forcefield wasn't obvious. 
- The enemy knows your SFX.  If Electroweak Man's forcefield is bright and glowy, it shows the world (or at least the parts of it that can pass a SS roll) he has electroweak force based powers. 
- Everyone nearby knows if your combat powers are active.  Secret ID stuff, social stuff, disguise stuff, all sorts of fun implications. 
And more, this is just a minute's thoughts on obvious things. 

does he side with the cops?
does he kneel?