Fallout 3 or New Vegas is what you might be looking for. There are dart guns, plasma guns and grenades, nuclear bomb shooters, microwave emitters, laser rifles, flame throwers, gatling laser guns, Tesla cannons, Gauss rifles, mini chainsaw-like knives, a dinosaur-claws glove like thingy called Deathclaw Gauntlet, guns which shoot nails and steams like a train, bombs in lunchboxes, alien rifles and pistols, energy-ball throwing cannons, a gun which fires any garbage you find around, etc.
Then you have your normal weapons like assault rifles, missile launchers, revolvers, pistols, sniper rifles, shotguns, BB guns, hunting rifles, Abraham Lincoln's personal repeater, sub-machine guns, knives, baseball bats, wooden boards, lead pipes, swords, axes, shovels, spears, golf clubs, etc.
I would recommend you get the editions for both these games with all the DLC aka. GOTY. They all give you tons of new weapons.