Without summit registers on many formations, it sure is hard to know, isn't it?
Seeing as many of the crags and domes at the Balls are not technical summits, and close to the road, I would imagine quite a few folks scrambled up to the tops from behind long ago. Same goes for Squaw (Piyau) Dome (no summit register there still, right?), Jackass, and presumably Fuller Buttes. Also, can't imagine Eagle Beaks weren't summitted prior to any of the technical ascents.
It's interesting that Hawk Dome, a technical summit, did have a register prior to 1970, but is not longer there according to others.
I don't know of any rumored ascents, but I bet talking to the old fellow up at the Shuteye lookout would provide some good leads for rumored ascents by folks who may still be around to tell the tale. I hear he's quite the historian - and I can't recall his name at the moment.