Here's the best argument against Intelligent Design I know: teeth.
Seriously. If I were in charge of the universe, I would NOT have given humans just two sets of teeth. What the heck is the point of losing baby teeth at six, when they're hardly even broken in, and then letting mankind muddle through with just one more set of teeth for up to NINETY years? Do we need them any less than sharks?
Roald Dahl had all his teeth removed at 21, opining that they were more trouble than they're worth, and was a loud and frequent champion of that decision for the rest of his days.
I often think the man had a very valid point.