Combine the indicated items to create the corresponding weapon.

Air Horn: Traffic cone + Aerosol spray
Beer Hat: Bottle of beer + Hard hat
Blambow: Bow and arrows + TNT
Blitzkrieg: Assault rifle + Electric wheel chair
Defiler: Axe + Sledgehammer
Drill Bucket: Bucket + Drill
Dynameat: Human hand (or meat) + TNT
Electric Rake: Car battery + Rake
Exsanguinator: Vacuum cleaner + Saw blade
Fire Spitter: Tiki torch + Light machine gun
Flamethrower: Gas can + Super soaker
Fountain Lizard: Lizard head mask + Pipe
Freedom Bear: Giant teddy bear + Light machine gun
Gem Blower: Gems + Leaf blower
Hail Mary: Football + Grenade
Heliblade: Toy helicopter + Machete
Improvised Explosive Device: Box of nails + Gas can
Infernal Arms: Training sword + Motor oil (located behind the casino stage)
Letrci-Rake: Rake + Car battery
Light Saber: Gems + Flashlight
Molotov: Newspaper + Booze
Moto-Saw: Dirt bike + Chainsaw
Paddlesaw: Canoe paddle + Chainsaw
Pitchfork Shotgun: Pitchfork + Shotgun
Power Guitar: Guitar + Amp
Propeller Hat: Serve-Bot head + Propeller
Rocket Launcher: Pipe + Fireworks
Snowball Cannon: Extinguisher + Super soaker
Spiked Bat: Box of nails + Baseball bat
Tenderizers: Box of nails + MMA gloves
Tesla Ball: Hamster ball + Car battery
Wolverine Claws: Boxing gloves + Bowie knife
Zombie Eater: Push lawnmower + 2X4

Additionally you can create vehicle-weapon combinations after you unlock the motorcycle trailer by completing the "Here Come The Contestants" mission:

Chainsaw Motorcycle: Motorcycle + Chainsaw
Machine Gun Motorcycle: Motorcycle + LMG
Rabbit Motorcycle: Motorcycle + Giant Stuffed Rabbit (found outside on top of Moe's Maginations); earns 10 PP for every killed zombie