Pranksters, start your engines. Gizmodo lists eight tricks you can play on your iPad-owning, smug and self-satisfied friends to wipe the grins off their mugs. They've got a full gallery of options here; I especially like the SPOD screen, and the Wishful Thinking version shown here (multitasking! Flash! VERIZON!!) is quite funny.
If you like the Blue Screen of Death or the Bloody Hand (which is oddly reminiscent of a certain scene in James Cameron's last big blockbuster), chime in below -- or include links to your own favorite background screens.