^You actually don't need to abduct a child for Wilderness Run, go to Town Hall and ask for a kiddie pass. They'll give you a piece of paper that lets you on it, that's how I got it. And I'll be getting that cred if it's the Miner Mike I'm thinking of; I'm swinging by to nab it coming back from a visit with my girlfriend in March.
Fairly sure the rarest creds I have are the two at Stricker's that are open six days a year. It also took me fifteen years to clean out my home park because I could never get on Great Pumpkin Coaster. Crabbie Cabbie at Carowinds could also count since it has the same policy, though Mike Fehnel was awesome and let the Coaster Crew members get it when I went. My first cred (Python Pit at Jeeper's in Detroit) I bet is rare too.
Camden Park's creds might also be kind of rare, considering how it's a **** **** hole with a monopoly on the industry in the worst state ever and you probably have absolutely no reason to go there unless you've given up on life enough to risk your life for some crap creds in a crap park in a crap part of the world.