One who circles around a gas station waiting for someone else to leave a pump when all others are in use. This person will usually drive around two or three times waiting for the opportunity to take the spot.
Bob: Dude, we've been circling for hours, let's just go somewhere else.
Johnny: No! I don't care how long it takes, it's $3.45/gallon here, the cheapest price we've seen so far.
Bob: Dude, you're such a gas station shark...