Winter!: Prepare for holiday gaming!
If you're gonna introduce yourself to first-person shooters, this is the way to go.
Half-Life 2 hits all the core aspects of the genre: guns, zombies, story, AI, scary parts, exploration and adventure.
Team Fortress 2 is a great team shooter. One of the greatest parts about it is that even though its not an MMO, even now, four years after release, Valve is still adding new content.
Portal is a gem as I'm sure everyone knows by now. The physics puzzles, the dark humor, everything make it great.
Game Traits applied to The Orange Box [Half-Life 2] (PC) by Loonybin0