The combination of unusual tricep structure (also found in cats and the extinct great sloth), remarkably mobile shoulder structure (inherited from our primate ancestors) and grippy hands (thumbs!) gives us remarkable downward thrusting power useful for smashing, grabbing and throwing.

One of the earliest inventions, the spear-thrower, enhanced that ability even more, giving us the ability to kill big game from a distance with near impunity. (It works by increasing the lever arm. Think of a lacrosse stick.)

http://en.wikipedia.org/wiki/Spear-thrower