Amazon has been discounting certain games only for Prime members for a few months now. They don't advertise it except for a little blurb on the individual page for the game itself.
I discovered you can search for them on Google. If you type this phrase in the search bar it does a pretty fantastic job of sniffing them out:
site:amazon.com "Amazon Prime Member Savings"
New deals are popping up and old ones disappearing all the time. I thought we should have a thread here so we can crowd source this and keep a constantly updated list of all the Prime deals.
Here's the deals I've found that are currently active. If you find any new ones or if you discover ones that have expired feel free to post it here so we can keep an accurate list.