Remote - "it just works"
Facebook - only some features, the webapp has the rest
Myspace - better than the web version!!!
Shazam - I don't think people realize just how amazing this is. There will be probably be legal issues with this in the future...
Bloomberg - best designed app so far, incorporating accelerometer. When you rotate, it goes to a full screen chart
Jamd - photo stack feature utilizes multitouch well
Cube Runner - best free game