Eating spicy food releases endorphins. Go eat stupid hot wings or mexican food. Seriously.

Jerk off.

Choke yourself.

Jerk off while you are choking yourself.

Do whippets.

Huff paint.

Huff gas.

Huff Air Duster (the compressed air stuff you use to clean off your computer)

Stick a gerbil up your ass.

Go skydiving.

Take a swing at a cop.

Cut yourself.

Get a blowjob from a chick who knows how to do it really well.

Get laid.

Rob a bank. Take a hostage.

Race someone (on foot, in a car, on a bike, on a motorcycle)

Work out.