The most filmed? Golden Gate Mountain behind Old Tucson, beneath which The Duke and Dean Martin used to trade barbs.
Second most? Probably this one. It's called Sombrero Peak by the locals, officially known as Safford Peak, on the north end of the Tucson Mountains and south of Rattlesnake Pass. This is what it looks like at 8:30 in the morning, a distinctly non-magical hour when Mr. Sun is already on his second stack of waffles. I stuck a saguaro in it to make it slightly more interesting. On the east side of the range is the Lazy K Bar Guest Ranch. On the west side is White Stallion Ranch, and for decades they have duked it out as contender for the title of "Old Tucson North"--both host to numerous films and TV shows, from the esteemed Winchester '73 to the lesser esteemed The Lone Ranger and the Lost City of Gold, which isn't half bad, really.
I'm awarding the title to White Stallion, because the Lazy K Bar received approval this year for a 100+ acre, 178-home development. The north end of the Tucson Mountains is quickly being enveloped by man and fewer beasts. I try not to judge, because our own property backs up against Tucson Mountain Park near Gates Pass.
Still, if White Stallion ever sells out, that will be the end of a horse-drawn era. You can read all about the history of film in them thar hills in In Search of Western Movie Sites by Carlo Gaberscek and Kenny Stier, an excellent resource.