For me, it was a copy of the exceedingly rare FUNNIES ON PARADE, a comic book prototype that predates the first newstand comics. I was the winning bidder at a reasonable price until the very end(I thought). But with one second left, I hit refresh on the auction, and it now listed some other guy as the winner with a bid that was three pennies larger than my high bid! It was literally at the very end of the auction. :(