Heith

Heith is the Slash ship between Hunk and Keith from Voltron: Legendary Defender.

Canon
It is implied that Hunk and Keith were familiar with one another during their days as cadets at the Galaxy Garrison, but their exact history is unknown. It is possible that their connection was limited through a mutual connection to Lance, who is Hunk's best friend and apparent rival to Keith.

Their first onscreen interaction is when Lance, Hunk and Pidge are helping Keith to rescue Shiro and escape from Garrison personnel. Their team dynamic is established right away, with Keith telling Hunk to lean right and left in order to help his speeder turn.

Despite their opposing personalities, Hunk and Keith get along very well. Keith reacts positively when Hunk hugs both him and Lance and proclaims that forming Voltron gave them all a brotherly bond. Later, at a party, Keith is seen laughing out loud when Hunk is being goofy.

In the show's second season, Hunk and Keith go on a mission together to get scaultrite from the belly of a Weblum. The whole episode is dedicated to their mission, and their bond develops. Hunk is questioning Keith about his newly discovered Galra heritage, sometimes annoying him, but not to the point of conflict. Soon, Hunk realizes that Keith isn't prickly and serious all the time, and is capable of making jokes. Keith's pragmatic and stubborn nature also calms Hunk down when he starts getting nervous. During the rest of the episode, they are seen working together to complete their mission, and at the end, Keith makes a point to thank Hunk for his hard work an bravery.

Hunk teases Keith about his Galra heritage a few more times, but again, never to the point of conflict. its obvious that Hunk is not truly bothered by Keith's Galra heritage, joking about how "Galra Keith" is a lot more fun than "Regular Keith." When Allura is giving Keith the cold shoulder and refusing to acknowledge his work in the Weblum, Hunk speaks up to remind her that Keith was part of the mission too.

Fanon
Though not as popular as Klance, this ship has a pretty large following, and grew steadily between the first two seasons.

Fans like to theorize about their past at the Garrison as well as their possible future relationship.

Most analysis for the ship comes from Keith and Hunk's opposing personalities. Keith is impulsive while Hunk is cautious, Keith is serious while Hunk is more goofy, Keith is the offensive type while Hunk is the defensive.

Trivia

 * Tyler Labine, Hunk's voice actor, has said that Belly of the Weblum was where Hunk and Keith's friendship was fully cemented, and when Hunk realized that he fully liked Keith as a person.