Among a number of (usually uncredited) guitarists who have backed the Stones in the studio are Jimmy Page, Ry Cooder, Dave Mason, Eric Clapton, Wayne Perkins and Harvey Mandel (the latter two while auditioning to replace Mick Taylor).
Edit: Clapton's efforts were not officially released but I think one of them appeared on a bootleg of out-takes. Also, Rory Gallagher was invited to join the audition sessions on which Perkins and Mandel played but walked out after Keith left him waiting around in a hotel for a day or two. Probably just as well, really.