Well there are lots of witty quotes on this thread already... so i'm gonna give you guys a couple more:
Do not follow in my footsteps, i keep running into walls - anon
The direct use of force is such a poor solution to any problem, it is generally employed only by small children and large nations. ~David Friedman
and my all time favourite sentence, by phillip pullman, is not necesarily witty but just beautiful:
I spread my wings and touch ten million other worlds, and they know nothing of it.