I'm surprised nobody said "shoes." Wet socks aren't much fun, but I can grin and bear it. But once I've somehow got socks dry, it really rubs me the wrong way to stick my sock-clad feet into a shoe that hasn't dried out.

Wet gloves are bad, too, but I only have to put them on once when commuting. Much worse on a hot and humid day trip or supported ride when you have to put wet gloves on multiple times a day.