Human weapons:
Automated-Melee:
Chainsaw: Hastings
An old slow heavy chainsaw of metal(Not of plast like newer ones).
It would be real heavy and hard to retrieve ammo for. It would take down an zombie in matter of seconds, but with only ability of attacking one zombie at a time the owner would probably be killed, if at least 2 zombies attacked at once.
Circular Saw: Luci2327
Picture - Sawblade.
Could use up batteries pretty fast, and somewhat hard to find batteries amongst all the mess, left behind by the people whom lived there before.
Electric baton: Cheese
I think a electric stun baton would be a fun weapon to use against zombies. It'd be like the stun stick that the combine use. It would be good for keeping zombies at bay, rather than just doing damage.
Gras cutter:
Melee:
Alternate fire for metal based melee weapons:
The alternate fire would make you reach the weapon out, in front of you, and enable you to heat the melee weapon up over a heat/fire source.
For example, if the mapper adds a fire source, he can determine with an option if it should be possible to use that fire source to warm up the current weapon.
If that option is enabled, your crowbar/fire poker will be heated up by the fire source when you reach it out, allowing for much higher damage than usual, as it would burn the zombie with each hit.
Baseball-Nail-Bat: CopperCoatedCandy
Same as baseball-bat, but with an nail through it making it much more damaging.
Could be used with the nailgun on the normal baseball-bat, which is more realistic than finding one I believe.
Brass Knuckles: Koozie The Katt
Bread-Knife:
Would surely be the easiest weapon to achieve. It can be found in most homes, with shortest range of the melee weapons and an unknown amount of damage.
Cinder Block: acker
Secondary fire throws.
Combat knife: acker
Primary slices, secondary throws. Retrievable.
Cricket-Bat: Kevin_Ryman
Crowbar: Harrier
I myself would like to see a large crowbar. One that require 2 hands.
Slower, but you can stick the straight end into the zombie's eyesocket for a one hit kill.
Fists: LunchBox
Just your plain, good ol' fists
Fire-Poker:
Damage similar to what crowbar does.
It is to be found in most homes also.
Heavy firearms: CopperCoatedCandy
Using heavy weapons butt as a melee weapon. Damage depends on the weapon's size.
Katana: BOOM HEADSHOT (References from dejiko)
Damage: 50, 70 if you hit head.
Blade length: Between 61 and 76 cm.
Weight: ~1kg without the sheath (Said this on wikipedia, but i think it may be a typo of 10kgs).
A traditional Japanese sword, though they are now used mainly for display they are still deadly weapons that can easily decapitate a man. Can be found in a few stores or in homes.
Nightstick/Tonfa: Koozie the Katt
Paper Cutter: Koozie The Katt
Screw driver:
Skewer:
Can be found in most homes, though the damage isn't too good.
Could be possible to be able to carry several of these, for throwing purposes.
Tomahawk:
Whip:
Either a whip with one tail, or several, or both kinds. The melee weapon with the longest reach, not too good damage, but it will stun for maybe like 0,3 sec, besides the charge will take a little longer than with most other melee weapons.
I know, they'll never implement it, even though people can easily get a hold of it.
But it would have been so fun whipping the zombies around (Litteraly

).
Assault rifles:
COLT M16A1: GDB
M16A1 with 20rd mag. Very light, accurate and extreme fire rate (I think they were something like 800-100rpm), but not much damage. Good runner/scout weapon. If a M16 is deemed too hard to find, make it a cvilian AR15.
Colt M16A2: CopperCoatedCandy
Uses 5.56 caliber NATO in a 30-round magazine. Is the standard issue rifle for the U.S military.
Weaker than the ak-47(Due to lower caliber, I think), but more accurate.
Famas: memorium
FN FS2000: Feanaro
Heckler & Koch G36: bud389
Heckler & Koch HK416: Cheese
M16 with M203 grenade launcher: Kommando
I would like to see an M16 with a M203 grenade launcher in ZP: S.
Bolt-Actions:
ASM CZ-550: Koozie the Katt
.458 Lott, 3 round fixed magazine.
Kar(a)biner 98k: The_Infernal_Zombine
Mosin-Nagant: zephyr
Remington M700: CopperCoatedCandy
Scopeless.
Carbines:
Colt M4A1: CopperCoatedCandy
Carbine version of the M16, uses 5.56 caliber NATO in a 30-round magazine.
M1 Carbine:
Used in WW2 and Korea(Limited use in Vietnam). Uses .30 cal, or 7.62 in a 15 round magazine(I think).
Ruger 10/22 .22LR: acker
The original, non-hacked version.
Ruger 10/22 .22LR (Illegally converted): CopperCoatedCandy
Illegally converted full-auto Ruger 10/22 .22LR carbine with a 50-round drum magazine. Many shots to kill a zombo, but high rate of fire and large mag capacity. I'm way ahead of you though, there are a ~~~~~-ton of manuals and dvd's out there that are sold on the internet that show you how to convert a 10/22 to full auto (Though it is still illegal to actually do the converting).
Conversion manual.
Picture (Gun in back).
Double Rifles:
.700 Nitro Express: Koozie The Katt
It's the biggest rifle I could find. Maybe from the local neighbourhood Safari hunter?