Demolitionist

The Demolitionist is an NPC vendor that will spawn once the following criteria have been met: Once the Demolitionist has moved into a house, he will sell the following:
 * There is an empty house.
 * You have either a Bomb or a stick of Dynamite in your inventory

The Demolitionist's appearance seems to be based on dwarves from many games, films and works of literature: he's significantly shorter than other NPCs and wears a beard. Furthermore, his mining helmet, lantern, and the fact that he sells explosives fits the trope of dwarves preferring underground environments.