Recently, I looked over (but declined to review) a US$9.99 dictionary application. Despite one particularly lovely visual effect, I found it hard to define an audience for the product and thought the price tag hovered on the high side for an awkward app that didn't really do anything useful. In light of that almost-review, I'd venture to say that It's Playing, at $3.99 on iTunes, seems vastly under-priced.
I've used quite a number of media player apps over the past few years but none of them feels as tightly put together and with as much consideration for the user as It's Playing. This is a well-featured app that can play most every format you can throw at it and offers hardware decoding for MP4 and MKV files