CoD4!
I am happy to have found my Call of Duty 4 player banner from Gametracker.
click for larger image
I am usually not good at multiplayer FPSes (I suxx0rz at Counterstrike), but with CoD4 I found myself getting better and better through time. I started being last to second-last place on every game. Now I am almost always in the middle of the pack, sometimes ranked fourth of fifth.
I guess the game not just demands quick reflexes (something I lack) and shooting-in-motion sk1llz, but also a sense of geography, keen observation, predictive abilities, and a judicious choice of weapons and perks according to map type.
(Yes, I try to make it look cooler than it actually is ;))