Of course, free stuff like Google Earth and The Lab, though I don't push The Lab as much as I should.
Frontline Defense is great at only $0.04 and I'm going to start pushing the Heroes multiplayer version for people that come in looking for shooters like Pavlov and Onward.
Loco Dojo is fantastic. It's amazingly fun (although I hate the ? spaces on the wheel and the bridge block). It will get a group of four people into a game and I don't have to swap them out for almost a whole hour. Getting them into a match is relatively easy compared to other 4-player games out there. At $0.06, it's cheaper than other 4-player games like Raw Data and Arizona Sunshine.
I wish Shooty Fruity made some changes to having a lower height of the guns for really short players as well as made weapons auto drop, but still, it's a great fun shooter for intros (like Space Pirate Trainer but at half the price).
Furious Seas and Evasion, basically the same answer as Loco Dojo, they're both $0.06 and are multiplayer (but Evasion is only 2-player).
