Although it doesn't last long, the katana's one of the best bladed weapons in the game. It'll take down most zombies in one hit, slicing them in half like a hot knife through rotten, undead butter. And unlike some other very powerful weapons, you can actually keep this one in an inventory slot - perfect for when Frank finds his back against the wall and his front faced with hordes of groaning, shuffling shoppers.
The main reason it makes our list of effective weapons is because it's so easy to find right at the beginning of the game. Once you get through the warehouse, head right and upstairs to Roastmasters. Jump through the window on the far left to the awning below to find one of the razor-sharp swords waiting for Frank.