Darksiders II is $18.75 on Amazon right now with the (one time use) OCTOFUN1 code at check-out.
Spec Ops: The Line is
$7.49 $5.99 (with code 2GFT82012) through Gamefly. Steam game so you're still just buying the Steam activation code.
Edited, Oct 5th 2012 8:59pm by Jophiel