One of my absolute favorites is when Magneto removes all of the iron from guard's blood in XMen 2. Such a simple kill but it really shows the true power of Magneto.
Brody from Jaws finishes the freakin great white shark with a bullet creating a explosion with the oxygen tank in his mouth.
The shark disintegrated leaving the remains either to be eaten by a fish, shark, or to float to the bottom of the ocean. That's one shark that found out the hard way it bit off more than it could chew, and when you screw with a man's family it's moving towards a tornado.
It was tested on mythbusters that it wouldn't result in that kind of explosion.
Not to say you could never have a explosion involving a oxygen tank just what you saw in the movie,
Tony Montana (Scarface) coked up mowing people down with that machine gun screaming "When you mess with me,you mess with the best" as he is getting blown away.