Who ever said that goldfish were the lamest pets ever? Sure, they were, in the days before the R2 Fish School ($30) fish training kit. Use positive reinforcement to teach your fish to swim through rings, fetch, limbo, and play soccer. The kit comes with everything you'll need (except the fish, obviously). And yes, it works - we spent about an hour staring slack-jawed at the videos.
Which does NOT mean that we were trained to do anything by the fish kit, thank you very much.