Is there a guitar for the PS3 that works with both Rock Band and Guitar Hero 3?

NO

Yeah the guitar from GH3 is the only GH guitar that won't work with both.

"The game features special Rock Band-branded guitar controllers modeled after the Fender Stratocaster to be used for the lead and bass guitar gameplay; these are similar to the Guitar Hero controllers. The Stratocaster controller has 5 additional fret buttons of smaller size located further up the neck. These buttons can be used in special solo sections to play all notes as hammer-ons and pull-offs, with no strumming necessary.[20] Additionally, the controller features an effects pickup switch that can toggle between five different effects (none, wah-wah, flange, chorus, and echo for the Xbox 360 and PlayStation 3 versions; none, doubler, slap back echo, medium echo, and long echo for PlayStation 2[29]). The controller will be offered in both wired and wireless versions.[17] Overdrive for guitarists can be deployed by holding the controller in a vertical position or pressing the "Select" or "Back" button. Rock Band features a "Lefty Flip" setting, supporting left-handed guitar players; additionally, the strap peg on the Stratocaster controller can be moved to the other arm of the guitar, allowing comfortable use of the strap by lefties. Harmonix has confirmed Guitar Hero guitar controllers and additional third-party controllers are compatible with the game,[20][17] with the exception of the PlayStation 3 Guitar Hero III Gibson Les Paul peripheral.[30] (see Guitar incompatibility issues discussed further). No console-specific version of the Rock Band Stratocaster guitar is compatible with Guitar Hero III on that console.[31]"

Nope, sorry!

I'm sure some company will make one as soon as the copyright of the rock band guitar runs out though.

no they don't seem to be properly suited. Its a shame that they arent. yet some thing to do with patent rights between the makers. We went forward and offered an further for Rock Band. i'm happy we did.

Probably not for the PS3... You should check out the 360 though.

I was under the impression that the X-plorer was.

at least for the 360.

it is compatible.

I would assume the X-plorer would be compatible with PS3..

But.

i have seen lamer.

so..

maybe not?

no there isn't because 2 different companies that made them