How about non-matching socks? LittleMissMatched.com sells you paired socks with different colors and designs. “That way, you would never have to worry about losing a sock,” says one company spokesperson [exam question: does this violate an axiom of choice theory, if so which one?]. The company, by the way, considers schoolyard bullies to be one of its greatest opponents. Here is the full story, New York Times password required.
It is not the case that each sock is strictly unique; the company is encouraging its (intransitive?) young customers to trade socks with each other, to obtain matching pairs.