If you're willing to ignore the main quest line and side quests (and that damn ringing phone) then you can just roam the central plaza, killing zombies with what ever you pick up. The best choice in my humble opinion is the laser sword. Over at One Little Duck Bingo you can find the gems and flashlights needed to build it.
Alternatively you can rig Leons motorcycle (after you kill him in a Psycho mission) with a chainsaw found in the scaffolding of the stage. From there you spend your time merrily mowing down zombies.
Finally, you can just get this while playing the main quest line, though you would have to go out of your way a little bit to kill a fair number of zombies in your path, or even some not on your path. Overall, combo weapons are the way to go with this method. The more complex weapons will crank out high kill rates, but honestly just your basic spiked bat will do the trick. Use whatever you feel most comfortable with.