Sublime. If you don't have The Orange Box, you really need to pick this up. Mind you I haven't played Half-Life 2, any of its' expansion episodes, or Team Fortress 2. I could easily make this recommendation based just on Portal, the excellent and completely unexpected little game included in The Orange Box. Why is it so good? Read on...
Spoilers Ahoy!
Portal is a shooter, and yet you don't really shoot anything. You open holes in the world, aka Portals, as part of a maniacal lab experiment by an all seeing artificial intelligence, which is quite amusing. It's really a puzzle game, and at least during the first play through not very hard, I think I completed it in about 3 hours of play time, but you haven't ever played a puzzle/shooter like this. I could be wrong, but I can't remember one. The basic premise is that you solve tests by opening 2 portals at any time and making stuff in the environment change so you can reach the end of the test. I won't spoil the rest, part of the fun is discovering the game on your own. Once you have finished it, and your not sure if it over, the game ends and the song starts. This is what pushes it past merely excellent into one of those games you just have to play, the song is absolutely hysterical.
