There’s a temporary Promotional claim code good for $2 off any Digital Video Games Purchase at Amazon. It will be live until their Deal of the Week gets restocked.
The code is SQRLUVIO
Might be best for DLC, such as Kung Fu Strike – Master Levels DLC, which would be $0.99 after the code. Uses Steamworks.
Edit: I bought this, which ended up being free after the code (one-time use). Saints Row: The Third – Shark Attack Pack DLC