A trip to Crislip's Home Saloon in North Plaza will net you the excavator, which is basically a big drill. The beauty of this weapon is that it lasts a very long time, and you can basically cut a swath through crowds of zombies while wielding it.
Just aim at one zombie to attach him to the excavator's drill bit. Now use his flailing arms and legs as weapons as you work your way through the crowd. As you kill more zombies, your original victim's body will deteriorate, making him less and less effective. Eventually you'll want to sling him off the drill bit and get a fresh body on there.