I would fear the person behind it more than the gun I think. A 6' ft tall or larger individual would be pretty intimidating with a large gun. If just basing it on a gun then a larger caliber revolver, black hawk or SP101, or a 1911. I love the line in Grand Torino when walt pulls the gun on those kids,"Did you see the size of that HAND CANNON!" HAHAHA!
You believe that there is one God. Good! Even the demons believe—and shudder. James 2:19
"I do not fear the man that practices ten thousand kicks one time, I fear the man that practices one kick ten thousand times." Bruce Lee