I have been signed up by a friend to last.fm, where you can listen to the favorite songs of any of its members. Johnny Cash rules in my corner of last.fm, mostly because 'geek', 'mid-century hardball' and 'slavishly follows hipster fashion' all overlap on my musical Venn diagram. One of his songs has the line:

I've been living on muscle, guts and luck

All the best words have a 'u' in them, in my opinion, an opinion based to a large degree on the colour of the letter. Where 'e' is red or burgundy, and 'i' is yellow, 'a' white, and so on, 'u' is either a delicate light blue (Charlie Chaplin's eyes, for example. They are responsible for most of his affairs, or at least the shock of a first meeting with Chaplin in living colour after knowing his black-and-white form so well) or a gunmetal gray like the suits worn in Strangers on a Train.

The following words are light blue:

prune/tune/picayune (see if you can work out what stripes 'picayune' has)

mumps, but not lumps

stub, but not shrub

Lull, pull and mull are halfway between light blue and gray.

Lumps but not mumps, shrub but not stub, and Johnny Cash's line are the rugged gray. 'U' is the only letter that has both a colour and a black-and-white version, which is probably why all the best words have 'u' in them: such a versatile letter.