Aerobatics
Some of the cutting-edge commercial flight schools offer elementary acro as part of their course. FlightSafety in Vero has included acro for ten years. It started by giving CFI students spins, unusual attitudes and rolls in either a Decathlon or Citabria - I don't remember which. Then, they added it to the Commercial Multi course using an Aerobat. Now, they use a Zlin. I'd bet that FSI would work with you if you wanted to take on a Part 61 basis what they offer to their commercial students.
I know that taking some acro and unusual attitudes does wonders for your confidence and bolsters your piloting ability. I had a friend who was on final on a hot day in Albuquerque. A sudden dust devil flipped him over. He had an acro training flight the day before and instead of trying to fight the uncommanded roll he just let the airplane complete the roll and right itself. He told me that but for his flight the day before he would not have known to do that.
If I had it to do over again, I'd take acro.