The Juggernaught battle with him, Rogue and Psylocke showed the knives going in the only place where they would help the situation - under the behemoth's helmet so it could be removed, so on and so forth till the end of the battle. Once again, Longshot was portrayed as wildly flinging them, seemingly letting his Luck (an actual power attributed him in the Marvel Universe write-ups) determine where they connect. This sounds like Find Weaknes to me, with a lot of color that wouldn't necessarily need to be worked into the cost one way or the other.
Speaking of that write-up, I'll try to find it tonight and let you know of anything that may contribute. Like Iceman, this character could probably best use a small VPP to keep up with all the power stunts - like the She-Hulk entangle.