Quite a fun little game you've created. I don't understand why everyone here is complaining about the weapon strength. It seemed fine to me. Heck, the last sword would 2-hit some of the zombies. It's a great game.
To everyone getting stuck with being overcrowded, use the fences to your advantage. They can't pass them. Use your stomp on one side to stun then, open the gate, smack them in the face, then run back. Rinse and repeat. Also, don't keep blowing all your money on the next weapon. Save up and skip a few weapons to get an uber weapon. I think I saved up from the third melee weapon all the way up to the last one, and there was a big difference there.
All in all, a fun game. The only thing I'd like changed is the materials system. They become useless towards the end of the game. Perhaps if you make another, give the player control of what the materials are spent on as well as giving them options. For example, instead of the gates to other areas, maybe the player would rather hole up in a super-fort. The advantage would be that they're always revivable, the disadvantages would be less resources found and a possible trap if the zombies manage to break through. Good job pal