Perhaps I'm perverse, but I get some enjoyment from SNAFUs, like actors suddenly appearing in different clothes in the same scene.
Two favourites: Sophia Loren doing up her zip in El Cid, and Lawrence of Arabia reaching for offered food with his left hand.
I'm less amused by idiocies like The Hulk throwing tanks around like frisbees, or the aliens in Independance Day having the exact same USB connecters.