I'm looking at my old copy of "The Book of Lists," which has a list of the "10 Most Beautiful Words in the English Language" and a list of "The 10 Worst-Sounding English Words." (The lists are from different sources, in case you're wondering about the lack of parallel titles.)
10 Best: chimes, dawn, golden, hush, lullaby, luminous, melody, mist, murmuring, tranquil.
10 Worst: cacaphony, crunch, flatulent, gripe, jazz, phlegmatic, plump, plutocrat, treachery.
With the exception of "jazz" -- which just doesn't belong on the "worst" list -- all of these words align sound and meaning. That is, the words that sound beautiful mean something beautiful, and the words that sound ugly, have a negative meaning as well.
So here's the challenge: come up with words that sound beautiful but mean something ugly, or sound ugly but mean something beautiful.