What are some of your favorite fish you keep/have kept and why? Any oldie but goodies? Any "exotic" fish you own/have owned that you absolutely love? Any impulse purchases that didn't have a lot of thought which turned out to be favorites?
I'll talk about two of my favorites... The lawnmower blenny and the cinnamon clown.
I had done a fair bit of research about lawnmower blennies and absolutely HAD to have one. I love the way they look and their behavior. I bought one from somone on the forums and was so excited to see it's behavior in my tank. Unfortunately it jumped out of my open tank 2 days later

. I
SO want another but I know it'll happen again in my current open topped tank...
My other favorite was the cinnamon clowns. They looked nice and all but the reason I liked them was because of how aggressive they were towards me. I think the "relationship" I built with them was strong. I'd be working in the tank and they'd draw blood... I repeatedly had my mom (and some of the people who bought livestock off me) chase them off with the algae wand as I had my hands in the tank. Nasty little buggers but I honestly missed them when the 120g was taken down

. I forget the name of the person who bought them off me (you bought things off me a few times). Let me know how they're doing...
So what are some of the favorite fish you've kept, and why?