I'll remember these 8 common mistakes from movies.
SHOOTING SIDEWAYS Your gangstas just have to be different. So they aim their handguns sideways and hunch over and kind of glare along their arm in lieu of actually aiming. In fact, when they do this their eyes aren't even looking at the site but at their victim. Intimidating your intended victims is all well and good. But it comes to naught if, when you finally start busting caps, you miss the other guy by six city blocks. There's a reason we hold guns vertically. It's a more natural pose considering that the barrel of a gun is going to leap up and back when each round goes off. It's a lot easier to lower that site back to it's original position than it is to go searching for them over a 180 degree radius. Ever see Davey Crockett hold his flintlock sideways? This way is just plain dumb. [More]
Of course, you can always stick to a slingshot.
As for me, I think I'll bore things to death.