Definitely bamboo cat sharks for the win. So very friendly and so easy to train to hand-feed, only pharyngeal teeth. Best foods are mollusks, clam strips and squid cubes.
I saw one kept in a 90g with more than enough room, it was a shallow and wide one, though. I actually helped take care of "Jerome" for an entire summer, he was the smartest and most personable fish I've known yet. He also had a domino damsel living with him that he never bothered in the least.