Cool thread. I'll weigh in with the Taco 66. Let me preface though, we all are sentimental about the bikes we had as kids so maybe I'm biased on this ... but I think, aesthetically, it is the best looking. It has the double cradle frame, rear shocks and just the right spacing of the engine and gas tank within the chassis. The two shots I attached definitely catch the best angles. The compact two-stroke AH-58 fits in perfectly and had a more exotic appeal than the trusty Briggs. Others have already attested to the purple frame. I can still recall, one look at that ad and I wanted to ditch my Taco 22 and get one!
Which I eventually did ... after totaling my poor 22. And having owned one back then, I can attest that trying to combine the jack-shaft and swing arm pivot was a terrible design. It was only a matter of time before it would come undone ... usually after launching it off a jump or curb.
BTW - finding pics of a Taco 66 is like hen's teeth. No doubt due to it's short model lifespan of a year or two.