See what's in your neighbour's rubbish/trash
(Amusement Potential: 20-30 minutes)
You can learn a lot about people by what they throw out. You might uncover some dark secret about them. Plus, they might be throwing out something with value that still works, like a VCR or some porn mags.

Watch TV, repeat everything said in Italian accent
(Amusement Potential: 5-10 minutes)
Sort of entertaining. Include flamboyant shoulder shrugs for added impact, or go for a Marlon Brando set of grunts.

Send spooky emails
(Amusement Potential: 15-60 minutes)
Look up someone's CV on the web, do some research on them via Google and then send them an email full of personal references claiming to be an ex-work colleague who fell in love with their shoes. Or something.

Make prank phone calls
(Amusement Potential: 20-60 minutes)
Very entertaining, but requires discipline. Remember - vulgarities don't make a call funny, but getting the other person to believe a ridiculous story will. Try seeing if you can get them to make noises to 'test' the line. One to get you started off: Call McDonalds with weird complaints about their food.

Pretend all humans will die except for people in room with you
(Amusement Potential: 10-20 minutes)
What would you do if this really happened? Would the group stay together, or would there be factions? Who would join what group? Remember, there would only be power for a few days before the plants ran out of fuel or broke. To travel, you would always have to be near cars to siphon gas out of. Best to do with people you know.

Step off a curb with eyes shut, imagine it's a cliff
(Amusement Potential: 2-5 minutes)
To get any benefit out of this one, you have to have a good imagination. Don't step off immediately, build up to the jump. Study the ravine below. Feel the winds at that altitude. Step off and...AHHHHHH!!!!!

Try and sound Welsh
(Amusement Potential: 1-3 minutes)
The key to sounding Welsh is to make sure that your voice goes up at the end of the sentence, so that everything sounds like a question. Throw in a superfluous 'isn't it?' at the end of everything you say and you're halfway there. Isn't it?

Burn things with a magnifying glass
(Amusement Potential: 5-30 minutes)
Ants are always fun to use for this, but burning the face of someone you don't like, under some circumstances, can be just as entertaining.