Halo 3 and the original MW2 was probably my heyday in FPS - young enough to both have the time to play silly hours of it and the reaction time also. Though the game I was best at, probably a shock to no-one, is Gran Turismo sport. I've put a lot of time in to other GT games and countless other racing games but GT Spot was the one I probably got the fastest and consistently fast in due to the FG leagues meant I played it the most.