I've got a very large crab that would probably make a great pet for someone that is willing to make a home for him. He came as a hitchhiker on some live rock, and grew from probably dime-size to the hulking mammoth he is today. If you held out your hand he would fill a good portion of your palm.
I don't have any kind of exact species identification, but he's the generic "gorilla" crab. Large black-tipped claws. He's never eaten any fish (despite the availability of fish that are smaller than him), but he does eat other reef type inhabitants, particularly snails. There are numerous corals in the tank that he came out of, so as far as I know he doesn't eat any of those. He'd be most suited for either a FOWLR or a dedicated system.
He is a very active architect - he thinks he owns the entire tank. He will move very large rocks, dig holes, etc. He doesn't like to crawl around in the open a lot, so that might cut down on his appeal as a pet, but we could almost always find him hiding just out of site under an overhang somewhere.
Anyway, I've spent a lot of money feeding him

so I wouldn't mind getting something out of the deal in trade or what have you.
Let me know if you're interested, I'd like to get him to a new home as soon as possible, since I'm sure he's not happy in his current holding cell.