Yeah, there are loads of "signature" guitars which are just tweaked versions of standard models - especially the hundreds(?) of different Fender artist models.
There aren't so many where the artist influenced the design from the ground up. I can't think of many with the artists' names, but I can think of a few artist designs:
Nuno has his Washburn N4 models, and he also had the more Les Paul-ish P4/Princess models. I don't know if he actually came up with the "P" body shape though.
And (the great) Rick Derringer co-designed the BC Rich Stealth, later used by (the late) Chuck Schuldiner.
And there was the Patrick Eggle Tony Iommi model, which had his name but he never seemed to use it much.
