Today, Valve has discounted a bunch of whole catalogs of games tied to individual IPs. They have bundle deals on FEAR, Gothic, and Star Wars. They also have a number of smaller things on sale. Here's my picks, as usual.
Terraria: $2.49 - I've recommended this before, and at $2.49, it's a great impulse buy. The game mixes some "Metroidvania" style platforming with building and exploring a la Minecraft. It's also updated with new content fairly regularly and in fact just got a huge upgrade.
All Dawn of War games: 66% off. I normally don't even like RTSes, but for some reason, this series just works for me. I think it's the territory-based resources or something. Regardless, lots of fun and a good deal today.
Disciples III: $4.99 - If you like the Heroes of Might and Magic or King's Bounty series of games and aren't aware of the Disciples series, this is more in the same vein. By far the prettiest strategy game of this type available, and incorporates a bit of King's Bounty style tactical movement, too. Fun and well worth playing, if a bit repetitive after a while.
What I'm getting: I snagged the Gothic series. I've had some friends bugging me to try these games for a while, so now I guess I'll give 'em a shot.