Gamestop has a ton of games selling for 19.99. Alot of these are price drops which have all come into effect recently, some are actually deals.
Bionic Commando for both XBOX 360 and PS3
Star Wars Force Unleashed for all systems.
Chrono Trigger(which this one is actually a price drop to 19.99 anyways.)
All Guitar Hero World Tour Band Sets are 100 dollars off if you happened to miss the Amazon.com one day sale GAC listed.
You'll pretty much have to wade through the listings of games to find which ones are deals or not. Again, most aren't, but there are good deals to be found(like Bionic Commando listed above.)