It is astounding how many times a handline over a bush or rock will save your ass.
http://hwstock.org/bish/html/IMG_7573.htm
I've been at the top of a 5.6 pitch when a friend cramped up and couldn't bend his knee. OK, time for a Munter Hitch rappel off 15mm webbing. Practice this improbable stuff beforehand, and you will impress folks who think you are amazingly prescient, when in reality you are just a dumb f*ck who thought ahead. ;^)