Sara in 'Two Mules for Sister Sara' (1970)
Dagnabbit, if Sister Sara ain't the most unsaintly nun this side of the Pecos, I'll be a hootin', hollerin' hornie toadie. Played by Shirley MacLaine, Sister Sara nearly outdrinks, outsmokes, and outshoots co-star Clint Eastwood in this bang-bang Western, and she may be history's first cinematic sister to appear on-screen almost in the buff.
'Course, Sara ain't really a sister at all, but a prostitute masquerading as one. Turns out, she's trying to help Mexico fight off the invading French, and she manages to blow up an ammunition train and take part in a bloody battle before she and her beau ride off into the sunset together. There's not much of a moral to this story, spiritually speaking: While most cinematic nuns struggle with their vows, Sister Sara never actually took any. Still, it's too bad they never made a sequel: It could've been called "A Fistful of Rosaries."