Perhaps the most ridiculous rules interpretation issue I had the pleasure of sitting in on had to be when one of my fellow players, playing a cosmic-style teleporter, tried to teleport a huge nuclear missile to the far side of the moon.
When the GM considered the teleporter's teleport power level and the mass of the missile, he ruled that the character couldn't do it. The player railed against this, wondering what the GM meant by "mass." When the GM tried to explain what "mass" was, the player went ballistic.
I'm no longer certain how the discussion got into "mass" and "density," but it did. The GM tried to explain that mass and density were different, that density was the amount of mass within a certain volume. But the player insisted that mass and density were the same thing and that volume was a term used only in terms of liquids. When a third party observer brought down his high school science text book that explained exactly was "mass" and "density" were, the player called the science book "stupid."
To this day, my friends and I crack jokes about "mass" and "density" at the expense of this player.
A close second to this had to be another player who was a wargamer more than a roleplayer. Every time he built his character (a sorceress with a hyper-efficient EC for her spells), the GM would somehow be able to damage that character with an attack. Every time the GM scored a hit during an adventure, the player would go back to HeroMaker to completely rebuild his character to make her completely immune to the attack that harmed her that session. When the GM confronted the player on this, the player's response was that the program allowed him to do it so it must be legal.
Needless to say, I don't play with either of these players any longer.