My massive bubble wrap. This stuff pops SO loud.. every time you pop one, you feel like you've accomplished something more each time. =)
A sheet of thin plastic filled with air bubbles - thus creating a thing for endless hours of popping fun.
Highly knowledgeable doctor bloke: Bubble wrap, you foolish gimp!
"I'm bored. OOH! Bubble wrap! POP POP POP POP"