He had a hobby of safe-cracking. There's a funny chapter in "Surely You're Joking, Mr. Feynman!" where he recounts the lousy security during the Manhattan project. He would gather top secret documents or reports (usually ones he had permission to see, he just didn't bother to request it, IIRC) and leave notes like "Feynman the Safecracker borrowed Document ABC123", and as they upped the security, he would just keep managing to get access to the files.

It was usually silly things, like locking one cabinet drawer, but not an adjacent one, so someone with long enough arms could just reach into the cabinetry and get their hand inside the other drawer. Or just knowing the birthday of the person whose safe he wanted to crack, and 90% of the time that was the combination. I think in one incident, the safe was just simply left unlocked. But of course, Feynman doesn't disclose those little details to the people around him, and quickly became known as a lockpicking legend.

Edit: He also was an artist who sold several works, and an avid percussionist who played with groups in Brazil, and many other things I'm forgetting. I'd really recommend reading "Surely You're Joking" or any other book about him, his life is incredible and hilarious.