Guide: Wooden Bow with Wooden Arrows
Merchant: Throwing Knives
Nurse: Thrown Syringes
Demolitionist: Grenades
Dye Trader: Exotic Scimitar
Zoologist: Claws (Yes, this is because she's a werefox, and she even uses claws in her human form.)
Golfer: Golf Balls
Dryad: Dryad's Blessing, which buffs players and harms enemies
Tavernkeep: Ale Tosser (Confirmed)
Arms Dealer: Flintlock Pistol
Stylist: Stylish Scissors
Painter: Paintball Gun
Angler: Frost Daggerfish
Goblin Tinkerer: Spiky Balls
Witch Doctor: Blowgun
Old Man: N/A
Clothier: Book of Skulls
Mechanic: Wrench (Thrown)
Party Girl: Happy Grenade
Traveling Merchant: Revolver
Skeleton Merchant: Bones (Thrown)

The first three are weapon upgrades for pre-Hardmode NPCs.
Guide: Wooden Bow with Flaming Arrows
Arms Dealer: Minishark
Traveling Merchant: Pulse Bow
Wizard: Flower of Fire (Inflicts 'On Fire!' Debuff)
Tax Collector: Classy Cane
Truffle: Mushroom Spore (Stationary Until Touched)
Pirate: Pirate Cannon
Steampunker: Clockwork Assault Rifle
Cyborg: Rocket
Santa Claus (Christmas Event): Bauble (Thrown)