Nothing that was designed specifically for 6x6 film size. But quite a few that were designed for 6x7 or 6x9 will take a graflex 6x6 back.
horseman and linhof made folding technical field cameras.
Arca swiss, toyo, and gowland made 2x3 rail-style view cameras.
Graflex of course made 2x3 crown, speed, and century graphics.
There are also press style non-folding cameras mamiya press, graflex xl, and koni omega.
And there are some old woodies, korona and the like that were made for 3x4, not sure about 6x9
So, yeah, lots of options.