Freddy's Glove, without a doubt. But I don't get me wrong I do like chainsaws... and Candyman's hook is pretty cool too. But like Arioch said, Freddy's glove is the only real cool AND original one....

Chainsaw

as far as shear desructive power..the chainsaw would win(i've seen first hand it's affect on flesh and it ani't pretty).it's got heft sure,but it takes a minimal amount of skill to weld and it's got reach.leatherface's saw was about 3 feet long at last count.:)