Besides all of the gross returns people tried to do when I worked at an "Adult Toy Store"... (icky poo) I had a man try to convince me that his $65 unfiltered Brunello had "worms" in it... and even after I fished out an entire grape skin, unrolled it, and showed him conclusively that it wasn't a "worm", he continued to argue that it was bad.
People would often try to return wine on the merit that they hadn't liked it, or it "smelled funny" ... despite having drunk the entire bottle. The bottles were sometimes washed, so I couldn't smell for myself, but more often than not filthy and reeking because they sat in a hot car for days before trying to make a return. Yeah, it smells funny ... stale cooked wine tends to.
Oh, and trying to return a wine that was "corked"... because pieces of cork had fallen into the wine when they opened it. Those were my favorite, because we were allowed to skim the wine and take it home!!! ;)