Mine was GoldenEye 007 for the N64. I borrowed it from a friend I used to play it with, and then me and my father would play deathmatch in split-screen... I miss those old days of social split-screen gaming.

On PC though, my first FPS was either Unreal Tournament or Half-Life, can't quite remember.

Dosesn't really ruin anything, I mean, you might as well just turn the volume on your computer/TV higher. Besides, it's online, it's not always gonna be even fair play.