An old joke, but a good one. Sorry for posting it here, but it's too long for the "jokes" page.
Two guys are sitting in a bar when one turns to the other and says "Hey...did you know this is a suicide proof building?"
"Suicide proof building? What the hell are you talking about?"
So the first guy takes him up to the roof and says "Look, I'll show you." and he steps offf the ledge. The first guy looks on in horror as the smiling man drops down, but at the last minute he's sucked inside a window.
A few minutes later he's back on the roof. "See? I told ya! The building design has a special updraft built in. Whenever anyone falls or is pushed or anything, they never even reach the ground!" To show what he means, this time he jups again, but just to be a wise-ass he does a somersault and a swan dive, but sure enough, he gets sucked into the second story window again.
When the elevator opens up and the guy comes back onto the roof, guy number two says "You were right! that's amazing. Think of all the accidents this could prevent! This system should be on every building in America!"
"You would think that...but so far this is the only building that has it."
"Well I just have to try this!"
"Be my guest. You're as safe as a kitten with it's mother."
So the guy steps off, and dozens of people watch in horror as he hits the pavement, falling to his death.
The first guy goes back down to the bar, shaking his head.
"Hey, bartender, gimme another whisky."
"You know," says the bartender, "you're a real bastard when you're drunk, Superman."