Sling Shots can be very deadly. They are silent, do not produce a muzzle flash, can be concealed w/o much problem, and there is an unlimited amount of ammunition.
I had a wrist sling shot as a kid and could kill a rabbit at 30 yards with just one of my store bought marbles. Gave it up when my dad bought me a .22 with a 20 round clip. Guns were just so much cooler.
I've a wrist rocket for squirrel control. Regardless of the projectile velocity, fumbling around with a wrist rocket and a sack of ball bearings is no way to confront a criminal. You're dead before you can get the thing loaded.