Which Engine flew....
Which engine flew the most types? Types, that is....
My guess is it would be one of the smaller Lycomings or Continetals. Probably in the 65Hp class if you're going to count homebuilts.
But I fear the PT6, with it's vast array of variants might trump the deal.
So let's re-ask the question - which piston engine powered the most types?
And which turbine?