This occurs when you buy something only to discover that you could have got it cheaper somewhere else. Usually adding insult to your being as well as injury to your wallet
Ah shit, I got this dvd for £5 and now its here for £3. I hate cheap shots!
hotshot: (noun) 1. a liquid of high alcoholic proof, which when ingested repeatedly, transforms the drinker into a self-perceived hottie. 2. also works in reverse, creating the perception that all members of the opposite gender are hotties.