I guess I'd have to say my dad..
Once my grampa had two pigs with the same physical problem. (My dad says they were born without buttholes). The vet came out and fixed one of them. My grampa made my dad watch what the vet did, then Dad performed the same operation on the other pig. The vet's pig died, my dad's survived.
My dad has an 8th grade education. His father moved him out to my dad's sister's farm in Wisconsin when he was 13, because he was afraid either he or one of two of my uncles would kill each other. They were all a year apart, and got into real fights all the time. Even throwing pitchforks at each other.
He's quite handy. He's built his own house in which they still live. He even cut down oak trees on my grampa's farm, hauled them to the lumber mill and had them made into columns and floor joists for the house. Dug the basement, mixed and poured all the concrete. He was 19.
He was a self-taught gunsmith for 30 years. Had his own business that he ran in the evening after his day job as a tinner.
I was once on a golf outing with Master Builders of Iowa. Paired up with a sheet metal contractor from Dubuque, who asked if I was any relation. He told me that my dad was the best tinner in Dubuque, maybe even the state.
He built a pontoon boat -- made the pontoons himself. He built a camper that we used for a number of years.
He has a shop with lots of tools - metal lathe, sheetmetal brake, milling machine, band saw. The guy can make anything. He made a cannon not too long ago. Shot it this 4th of July, then scooted it back into the shop before the cops showed up.
When he wants to make some tool that he needs, he'll look at a picture of it in a catalog like Northern Tool & Equipment--then make it. Probably the smartest man I've ever met.
Funny thing is, he won't read a book -- just magazines. He says once he gets started on a book, he can't put it down until he's finished it.