Oh man, I've got you all beat! ....yes, I just turned coolest formula into a competition, so what?

Except it's not one equation, it's four. Guessed what I mean yet? Maxwell's equations! (in differential form). They tell you everything you need to know about the way electric and magnetic fields work, which extends to imply things like E field always comes out of a conductor at a right angle to the surface, and you can even derive the speed of light out of them.

What a great set of equations!

<img src="http://home.att.net/~newtuniv/max-diff.gif"> ...wow, it was hard to find a good picture of them

=A*exp(-Ea/R*T)

its what will make me the big bucks when i graduate

I like Fitt's Law.

Some info about <a href="http://ei.cs.vt.edu/~cs5724/g1/glance.html">Fitt's Law</a>, which I'd never heard about until now.