The Cornish Buffer and SHO must be up there considering how simple they are. And I reckon the EM Drive will be as well, the amount of times here and on other forums where people have said they've made it is massive.
I only think of the honeybee because just like the klon it has legendary status, warranted or not, and there aren't many real ones from BJFE floating around and the ones that are are stupid expensive. I think it's a nice light-medium OD personally, and very natural sounding.
Ya, I have plans on making one some day. Just have pin got around to it. Currently building a klon. They sound good to. I think my three fav drives as of yet are fetto, zen, klon.