This is Mego's 12" Magnetic Batman from 1978.
After substantial success with their 8" line of action figures, Mego started to go the "foot tall" route with some of their action figure lines. Superheroes were at the top of Mego's list for 12 inchers along with lines like Star Trek: the Motion Picture and the rock group, Kiss.
This particular 12" figure is somewhat unique, in that, it has magnets in its hands and feet. This makes it difficult for the figure to stand on it's own but allows for some fun play on the family fridge and what-not. Mego also produced a Robin with magnets, as well. This allowed Batman and Robin to perform heroic feats... circus acrobat-style. Hey, you could even take Batman for a ride to the supermarket on the hood of your car, if you were so inclined...thanks to his magnetic ability.
Mego, to my knowledge, never produced a 12" Magnetic Spiderman...which would have been an ideal use of the magnetic hands and feet feature. Mego, did produce a 12" Spiderman figure sans magnets, however.
One thing I find very interesting about this figure is the head sculpt. He has a very determined, grim facial expression that wasn't common to Batman figures from the 1970s. Most toys depicted him to be much more mild-mannered and friendly. This is not a Batman you want to mess around with...and don't forget, he's got magnets, too. Getting pummeled by magnets is not fun.
A complete 12" Mego Magnetic Batman should include his jumpsuit with attached cape, belt, plastic forearm covers, and plastic boot tops.