It has to be my fire eels, especially Norbert. He's 24" long and sticks his whole head out of the water when I come over. He's only fish I've ever owned that I can call his name and he comes (if he's not already there!). He's ridiculously friendly. However, my close runner up is my 17" giraffe cat. He just comes over to say hi all the time. He's not interested in hand feeding. He just wants to see what your doing in and out of the tank. And I am particularly attached to two of my discus who have been paired together for years now through diseases/ close deaths, several tank moves, separations of more than three months (due to the female almost dying), and all this while living in a community of discus. They could have strayed, but not once. This pair is more committed that a lot of people!