I have not done it but have read about it.
It is just a hobby and fun stuff. But the most common I have heard is grafting tomato into potato. The result is that it grows potatoes in the ground and tomatoes on top. OF COURSE that is what they claim...hMMMM.

I like hybridizing idea. But it requires lot of discipline and years of work..no kidding and fun stuff here.

A number of folks are using Maxifort root stock and then grafting the target variety on to them. The theory being Maxifort is a vigorous root, and will be disease tolerant during the growing season. I will be trying this on several plants over this Winter as an experiment.

Raybo