Three graduate students are on a trip in (insert your favorite obscure nonsensical primitive locale here) when they are captured an isolated tribe who decide to execute them with a crude guillotine. The first, a divinity major, shouts out "May your god spare my life and prevent this device from killing me!". Much to the tribes amazement, the blade fails to drop, and the divinity major is spared. Next, the English major is brought up, and of course, simply repeats what he heard the divinity major say. Again, the blade fails to fall, and he is spared. Finally, the third student, an engineering major is brought before the guillotine. As he raises his eyes to the heavens and starts to repeat the life saving mantra, he stops and announces..."well, there's your problem right there! If you tie the knot on the other side of the blade, it should work perfectly!"
Okay, not as geeky as the others here, but someone has to tell the worst joke on a thread...