For me it has to be using the power router. Some things can't be done without it, but the noise and especially the dust is something I really hate.
My 'shop is so small that if I don't clean up every half an hour I won't fit in myself any more. Cleaning up after hand tools takes a few minutes, just pick up the chips and shavings, but cleaning up after power tools takes ages as the dust gets everywhere. And the dust also spreads around the house on my shoes and clothes, which I don't like a bit more than my wife.
Pekka