Goblin Tinkerer

The Goblin Tinkerer is an NPC, who must be saved by the player after a Goblin army has been defeated. He will randomly spawn in open areas in the Cavern layer while you are exploring. The Dungeon contains a large number of open areas and is the fastest way to force him to spawn. Talking to him in this state will free him, and he will wander the area until he gets killed by any nearby enemy or hazard, or until you move far enough from him. After that, he will move into an available house like any normal NPC. Note that if he gets killed, you WON'T have to unbind another one (the same with the Mechanic and Wizard.)

Goblin Tinkerer has the option to reforge a weapon, tool, or accessory for a variable price in Gold.

Once the Goblin Tinkerer has moved into a house, he will sell the following:

Quotes

 * "Hey..what's [Mechanic] up to? Have you...have you talked to her, by chance?" (only when the Mechanic is present)

During Day

 * "Goblins are very easy to anger. In fact, they'd start a war over cloth!" (references that you can use tattered cloth to summon a goblin army or the quest in RuneScape)
 * "To be honest, most goblins aren't exactly rocket scientists. Well, some are."
 * "Do you know why we all carry around these spiked balls? Because I don't."
 * "I just finished my newest creation! This version doesn't explode violently if you breathe on it too hard."
 * "Goblin thieves aren't very good at their job. They can't even steal from an unlocked chest!"

During Night

 * "Hey, does your hat need a motor? I think I have a motor that would fit exactly in that hat."
 * "YES, gold is stronger than iron. What are they teaching these humans nowadays?" (in reference to real life where gold is a soft metal)
 * "You know, that mining helmet-flipper combination was a much better idea on paper."
 * "Yo, I heard you like rockets and running boots, so I put some rockets in your running boots."
 * "Silence is golden. Duct tape is silver."

When Homeless

 * "I can't believe they tied me up and left me here just for pointing out that they weren't going east!"(Referring to the fact that the visual in Terraria is facing South, and West and East are thus swapped from their usual directions)
 * "Now that I'm an outcast, can I throw away the spiked balls? My pockets hurt."
 * "Looking for a gadgets expert? I'm your goblin!"
 * "Thanks for your help. Now, I have to finish pacing around aimlessly here. I'm sure we'll meet again."
 * "I thought you'd be taller."

When Rescued

 * "Thank you for freeing me, human. I was tied up and left here by the other goblins.  You could say that we didn't get along very well."

Trivia
The "Yo, I heard you like rockets and running boots, so I put some rockets in your running boots." quote is a reference to Spectre Boots as "rockets" means Rocket boots and "running boots" means Hermes boots. This line is also a reference to the popular internet meme of Xzibit from 'Pimp my Ride'.

One of the Tinkerer's names, Dalek, along with other game elements, references the British television series, Doctor Who.