Half-Life on Steam. It was well worth the $10, although I'm wishing I had spent the same $10 on Half-Life Source instead. :( It's weird that they'd be the same price... :hmm:
For those who don't know, Half-Life Source is basically just Half-Life, but with much better physics and water...
I think most recently I just got Call of Duty: Black Ops for Xbox 360, and before that I got Halo Reach. I also tend to borrow games from friends, and the last two of those were Metal Gear Solid 2 and Metal Gear Solid: the Twin Snakes