Anyone try Bike or Die 2? It's a bit hard, but so much fun. There are tons of options to change, and thousands of free levels to download online.
http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=297288395&mt=8
$4
http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=297288395&mt=8
$4