The iPhone app Tap Tap Revenge has been downloaded 10m times

"In all, we have seen well over 10 million unique installs of our apps since the App Store launch (10 million on Tap Tap Revenge alone). Tap Tap Revenge is played a million times a day. Literally. That means well over 100,000,000 games played!"
Source: Tapulous blog, 22nd April 2009