Buster Sword

It's a huge freaking sword.

You can talk all you want about the practical stuff -- its heft, the difficulty you'd have concealing it, the fact that you can't wave it around in your left hand while filling in this morning's sudoku with your right -- but none of that makes a whit of difference.  It's a sword the size of a person. It doesn't have to be practical.  If you can so much as raise it over your head without causing your enemies to retreat in mortal terror, the problem isn't your sword, it's your choice of enemies.