Gutbusters
I do a lot of screaming at children in my planetarium shows. It really gets out a lot of frustration. If you haven't screamed at the top of your lungs to a room of 65 seven-year-olds, you have not lived. Trust me, it's awesome.
What happens is this: I ask a stupid question ("Mercury is hotter than your oven. If the oven is on is it a good idea to go inside?"). They yell out an answer. Sometimes they answer appropriately, sometimes they get all wise-assy and answer a stupid question with a stupid answer. No matter how they respond, a second later I scream at the top of my lungs in a horribly annoyed tone: "NOOOO! Stay out of the oven!! What're'ya crazy!!?"
The kids, in general, go wild. They laugh and laugh. Soon they get into it, and whenever I ask a stupid question they respond stupidly, just so I will scream louder. And everytime I do, they laugh harder.
I had a girl who laughed harder than anyone I've ever seen. It actually didn't matter what I'd say after a while she'd just be there cackling away.
At one point, through agonized breaths, she pleaded: "Please. Stop. No. More. Please. My guts are gonna fall out!"
OK, that got me laughing. The teacher next to her got laughing.
Not sure if there are any stand up comedians out there reading this, but if so, please vouch for me when I say: When you're killing, you don't back off. No presenter is going to say "Oh, they are enjoying themselves WAY too much, I'd better stop doing such a good job." Oh, no. I just POURED it on thicker than ever.
I thought the girl was going to die. Literally. Just stop breathing and die. That doesn't mean I backed off then, either -- hey, I have to give them a good show!
After the group left (she could hardly walk... still laughing on the way out) I realized that I could have made a horrible, horrible mistake. But I checked the seat she was sitting in. It was dry.