[PC] Reccomend-a-Game (and proper spelling)

quake series: Seriously. Quake 2 and 4 have some awesome single player action, and Quake 3 and 4 have some of the most fun DeathMatch modes around. The Quake series is really a must-have for the PC gamer.

Half-Life 1 and 2: and their mods of course. I have to say i have beaten the first HL at least 20 times, and HL2 near that many times. The modding community also puts out some very nice content for these games as well.

Counter-Strike: It may not have the flashy graphics of Counter-Strike: Source, but the gameplay is solid and the crisp feel is rather refreshing after trying to play the stylized Source version. The recoil is responsive and the models don't look like toys which makes this game a simple, yet fun shooter that you can find yourself getting lost in.

Others have mentioned the UT series which is another great addition to a PC gaming collection. I would also check out Deus Ex and the Diablo series for some games you will find yourself getting sucked into.

Jam it back in, in the dark.