Designer Jonas Carlsson depicted the most characteristic for the various applications for the iPad position of fingerprints on the display.
In Safari, I tended to hold the iPad with my left hand and scroll with my right index finger towards the center of the screen. I realized this allowed for close proximity when clicking on links. When reading something of greater length, I usually held the the iPad with both hands and scrolled with my thumbs.
In Mail, I typically held the iPad with both hands in order to thumb-scroll both the email list and the content.
In Fruit Ninja, there were few, if any, static prints. Even the menu items are selected by slashing your finger across them.
The bottom menu is essential to Fieldrunners; most actions start from there.
If you know of other iPad apps with unique interfaces, please let me know.