I've actually done quite a few of these before. A few add ons that I didn't see though
1) walk up behind a group of people at the mall and say "I'm gonna butt rape you all tonight!" while playing the POTC theme song
2) draw on your arm/wrist with red pen/marker. see how may people ask what happened
3) When someone says anything, say "That's what he/she said!" and run away