I have only bought two things and neither were very strange:

Chocolate candy labels for my wedding
Park Tool Toilet Paper Holder (wait that was Craigslist)

How about the strangest thing sold on Craigslist/Ebay? I sold my used kitchen sink. We got a better one free from my uncle, pulled the cheapo builder one out and sold it. I thought it was weird to be able to sell a used sink.