Look, we all love a good gatling gun. The single best part in any first-person shooter, like Valve's excellent Left 4 Dead, is when you pick up that Zombie Mower and get to trimming the undead population a little bit. But the gatling gun is not for the faint of heart. The gatling gun needs to be tamed, for it is a wild and beautiful beast. If you treat the gatling gun rough, it will treat you rough -- by which we mean it will fire you across the map like a gritty Angry Bird.
"So this is what my sperm feel like."
To exploit this glitch, you need to find a gatling gun on the map and bash it with your rifle a bunch of times. Strangely, the amount of force with which it will launch you is proportionate to how many times you hit it. That's right: This glitch operates on the same principle as your childhood BB gun.
As far as an exploit goes, the gatling gun glitch is mostly useless and usually only serves to fire the zombies a big screaming pile of you. But if you get it just right, you can use it to get to a few nominally inaccessible areas of the game. Like this big neon sign:
Where you're free to just sit and wait out the apocalypse from on high while the wave of undead consumes all of your friends -- those same friends who so callously mocked you for beating up a machine gun in the middle of a zombie fight.
It seems to work too perfectly for a mistake -- if it was just a physics error, why would the gun fire you proportional to how many times you've hit it? But it apparently was indeed a glitch, and not an Easter egg, as it has tragically since been fixed. Apparently it breaks the immersion somewhat when every tense undead standoff is interspersed with men frantically punching inanimate objects and then suddenly cartwheeling over the horizon apropos of nothing.