Interesting thread. I own an aerobatic Beech Sundowner 180. Yes, they made them. Cleared for loops, spins, split-S, immelmans, aileron rolls, barrel rolls, snap rolls. Very quick on the ailerons. Not bad really for a 2450 lb tourer. If you can find one, I'd recommend it. Not much more of an aerobat than a C150 aerobat, but with an honest 115 knot cruise and 4 places, it is a great family tourer. At aerobatic weight (2030 lbs) with only 2 on board and light in fuel, the 180 hp Lycoming can climb sharply at 1000 ft/min.
The only problem, they were exceedingly rare. I happened to get my hands on one! I have thought of trading down to a C150 as I no longer need 4 seats that often, and would like to save on fuel, and still have a bit of fun. But at the end of the day I decided to keep the Beech.
If you're looking at 2-seat aerobatic machines, you could also consider a Citabria or Champ. I also heard that clipped-wing Cubs with 100 hp Continentals are pretty good as well. A buddy has a 115 hp Citabria and he seems to have loads of fun with it.