A Toaster
Bread
This one is best for individuals
Inside works best, depending on what is being popped
Put the toaster where everyone can see it and have everyone sit down, in chairs or on the floor. The idea here is for them to stand up just before the toast pops. Put the bread in the toaster and push it down, don't tell anyone what setting you have used. Whenever they like, players can choose to stand up, but the winner is the player who stands up closest to the pop, but not after it pops. If you stand up after the toast pops, you lose. Play a second round and change the setting, it's up to you if you go lower or higher, and it's up to you whether you tell them which.
Scoring is, as always, completely arbitrary, you can award only the winner or award points on a sliding scale from winner to first person to stand, people who fail to stand before it pops should get nothing. Decide how you wish based on the number of players.
You can use anything that pops for this, but people seem to think they know how long toast takes. I have done it with those little toys that you press down and then they pop up after a while. I usually do a round with a balloon taped to the end of a foot pump and the next round with a balloon taped on the end of an electric pump. Not for the faint of heart.