There are a ton of great PC deals on Amazon right now.

Scribblenauts unlimited - $7.50

Spec Ops: The Line/Bioshock/Bioshock 2 (this one especially might be great for you since you seem to like modern shooters) - $10 (seriously, one of the best deals imaginable)

Tantalizing THQ Bundle (Homefront/Red Faction 2&3/Stalker/Space Marine/Metro 2033) - $10

Darksiders Franchise Pack (Darksiders 1 & 2 and all DLC) - $13.19

Just Cause 2 - $3.74

Dark Souls - $15

Batman Pack (Arkham Asylam & Arkham City) - $10

PS3 Journey Collector's Edition (not quite a great match based on your likes, but 3 amazing games) - $30

After digging all those up, I remembered there was a thread over in r/gamedeals that covered the Amazon sales. I think the above are the best deals or major standouts, but check it out to see if anything else catches your eyes.