Things you can do with absolutely nothing...
Push your eyes for interesting light show:
(Amusement Potential: 1-5 minutes) See a variety of blobs, stars and flashes. Try to make out things - is your subconscious trying to send you a message? Can you control what you see by pressing different areas with different forces? Would it be possible to somehow see the same effects on TV? Or for that matter, watch TV with your eyes shut doing this?
See how long you can hold your breath:
(Amusement Potential: 4-20 minutes) Not that much fun, but it sure passes the time. Play with a friend, or try to beat your own personal best. Some tips: hyperventilate before hand, and stay as still as possible.
Try to not think about polar bears:
(Amusement Potential: 1-5 minutes) This is especially hard, because by trying too much, you remember what you were trying to avoid thinking of. If you try too little, you end up thinking about polar bears anyway.
(Amusement Potential: 1-3 minutes) Go ahead, scratch yourself now. Even if nothing itches, go ahead. Doesn't that feel pretty good?
(Amusement Potential: 1-3 minutes) What is pain? Why is it unpleasant? There's nothing physical about it - it's all in your mind. Plus, after pinching yourself for awhile, boredom will seem nice next to being in pain.
Try to swallow your tongue:
(Amusement Potential: 1-3 minutes) There's not much to say about this one. It is possible.
Look at something for awhile, shut eyes, study after image:
(Amusement Potential: 2-5 minutes) Another great time waster. It takes about 30 seconds of staring to create an after image, and the image is then viewable for about the same length of time. Fun to combine this one with pushing on your eyes.
Get yourself as nauseated as possible:
(Amusement Potential: 5-10 minutes) Best achieved by looking straight up and spinning around. Try to be so dizzy you can't even stand up. This is also entertaining due to the "makes boredom seem a lot better" effect (see "Hurt Yourself").
Things you can do with very little:
See what's in your neighbour's 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.
Watch TV, repeat everything said in Italian accent:
(Amusement Potential: 5-10 minutes) Sort of entertaining. Fun to pretend the people on the screen are actually talking that way.
Call up people who write editorials you disagree with:
(Amusement Potential: 15-60 minutes) I'm surprised no one has thought of this before. Unleash your fury on the person who had the nerve to write a letter like that! I'm pretty sure it doesn't qualify as a prank phone call, too.
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. Even more fun if you get a bunch of people on the line using a Wonderphone and take turns making the calls. One to get you started off: Call McDonald's, try to make reservations.
Pretend all humans will die except for people in the 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!!!!!
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.
Things you can do with another person:
Have a water drinking contest:
(Amusement Potential: 5-10 minutes) While the competition is fun, you probably won't feel too good afterward. To give your event an old western theme, slam the cups upside down on the tables after you have emptied them.
Stare at the back of someone's head until they turn around:
(Amusement Potential: 2-5 minutes) This works on the "I have the feeling I'm being watched" principle. Conduct an experiment--does this really work?
Have a "Who is less competitive" competition:
(Amusement Potential: 1-3 minutes) Trying to win at this will make you lose. Trying to lose makes you win which makes you lose. Not trying at all makes you lose which makes you win which makes you lose.
Pick up a dog so it can see things from your point of view:
(Amusement Potential: 3-5 minutes) Think about it: your dog has only seen the house from a viewpoint from 6" to 2' high (15 to 60 cm for all you metric fans). It's never seen the tops of counters, what you keep on your desk, the tops of shelves, etc. Try looking at things from its point of view, too.
Pull out a hair, stick in someone's ear:
(Amusement Potential: 1-5 minutes) Best done to sleeping people. Added challenge in having no one else around, because then you can't blame it on anyone else. Try to beat your record number of times before the person catches on.
Pour water in hand, make sneeze noise, throw water on back of person's neck:
(Amusement Potential: 5-15 minutes) Always a good gag. For an even bigger reaction out of the person, act like you're not sorry at all for what they think you did. Comment instead on how big that sneeze was or about how there was a lot of mucus in that one.