Ear Force X4

Pros: Wireless, sound quality, feels like true surround sound, great microphone

Cons: price, but you get what you pay for

Summary: I use these for, what else, FPS. You can truly hear the direction of the sound (behind, left, right, etc.) with these. Microphone quality is a huge step up from basic xbox headset and never cuts out. In this review and in another review, CNET cuts on the IR range and sound isolation. I am able to walk around my basement, include into a separate room and still get full signal through walls. Second, who is really moving around, we are playing xbox, not Wii. In terms of sound isolation, unless you live next to train tracks, this is over-rated. Most people I know, and me, play in relatively quiet areas. That said, most normal level outside noise gets covered by the sounds of the game.
Ignore the negatives and pony up the cash.

I waited a year from getting my 360 to get these and wish I had gotten them sooner.