Adult Swim's Robot Unicorn Attack [99¢] had an update hit mere moments ago to add full OpenFeint support with both online leaderboards and achievements. If you've been annoyed by your inability to truly boast about your best runs other than posting to Facebook or Twitter, make sure you grab this update ASAP.
If you still haven't downloaded the game yet, it's still on sale for 99¢ and I really recommend picking it up. It's a quirky take on the see how far you can go platform game type that has become so popular on the App Store, and it's even available online as a free Flash game. The inclusion of online leaderboards answers my only gripe about the game, and I really can't recommend it enough.
Illusion Labs' Labyrinth 2 [$4.99 / Free] also saw an update today which aside from high resolution graphics for the Retina Display of the iPhone 4 and new iPod touch also added Game Center leaderboards and achievements. There are 36 achievements in all to farm, and if you're looking to fill up your Game Center achievement listing, Labyrinth 2 is an awesome game to do it with.
We loved Labyrinth 2 in our review, and really recommend at least trying the lite version out if you've yet to play the game yet. With Retina Display graphics and Game Center support, this is an already awesome game that just got much more awesome.