Pointui, the app that sits on top of Windows Mobile 5/6 in order to skin it into something actually usable. It's so awesome that I actually made a movie out of it, including Jesus-style subtitles, so that you guys can see just how awesome it is. (Have I said that it's awesome?) It fixes 50% of what's wrong with the surface of Windows Mobile right now, allowing you to get around the OS using finger swipes instead of a stylus. On your current hardware, no less. Who the fuck knew that Windows Mobile supported this?!
HTC did, for one, but their UI isn't quite as good as Pointui. In addition to enabling finger gestures, it also adds skinning on top of the standard Win Mo apps. Clicking the phone app, for instance, gets you a much prettier call log that aggregates calls from the same person into one entry (just like the iPhone). There are still other apps like email and calendar and tasks that aren't skinned—these just go into the regular WM app when active—but are much easier to get to.
The real winner is the system settings, which are made top level (instead of hidden under 3 layers of menus). It doesn't fix everything wrong with Windows Mobile, but it's free and it fixes a lot. We haven't gotten this excited about Windows Mobile in...ever. Holy crap. [Pointui]