Steam is currently having a Halloween Sale. Apparently any gruesome, spooky or weird games are on sale (so there's a lot of horror and zombie titles on sale).
I think the best picks are:
- Left 4 Dead for $7
- Left 4 Dead 2 for $7
- Overlord Complete Pack for $5 (hmm might get it myself)
- Vampire the Masquerade: Bloodlies for $5