I've recommended AVPlayer (HD) in several of my articles as a player with an excellent video decoder and feature set and one of the most recommended, best titles for iPhones and iPads alike.
Unfortunately, it (both the small-screen and the iPad versions) has been recently removed from the AppStore. I've talked to the developer. Currently, it's unknown when AVPlayer(HD) is put back to AppStore - it won't happen in the near future (1-2 weeks), that's for sure.
That is, in the meantime, if you haven't purchased AVPlayer previously and want to purchase a new player now, you'll definitely want to check out the alternatives. If you do know what file formats you want to play back, some of them: