Not exactly sure what you are looking for exactly...Are you trying to get recommendations on an app that lets you use the iPod's touchscreen as remote input for a computer? Or fulfill some other function?
I dunno about the "all time best" aspect of it but Mobile Mouse suits my needs just fine. You just need your iOS device and your computer (running Windows, Linux, or Mac OS X) to be on the same network and when you run the app on the iOS device, the cursor will track appropriately on your computer as well.