SunsetDash

SunsetDash is the femslash ship between Sunset Shimmer and Rainbow Dash from the Equestria Girls / My Little Pony fandom.

Canon

 * Near the beginning of "Rainbow Rocks," when Sunset and the other girls are warning Principal Celestia and Vice Principal Luna about the Dazzlings, the principals distrust Sunset at first, because of her previous actions. Rainbow was the first to jump in, commenting on how Sunset wasn't lying.
 * In the middle of "Friendship Games," Rainbow risked her life and the chance of winning the Academic Decathlon's Motocross Relay to save Sunset from being eaten by a plant monster, after Sci-Twi accidentally created magical portals. "I wasn't about to let my friend become plant food!"
 * Rainbow is also seen cheering on Sunset even after she loses the math portion of the Academic Decathlon.
 * In "Mirror Magic," Sunset is stressed about not having enough journal pages to write to Twilight, and Rainbow is seen walking by, saying "Chillax, Sunshim" while winking at her. Sunshim is a "movie star name" that Rainbow made up on the spot, but since Sunset is the only one she made one for, it can be used as a cute crush nickname in fanon.
 * In the short "Friendship Through the Ages," Rainbow is seen playing the guitar on a stage, and Sunset is being crowd-surfed. It's not confirmed, but it can be interpreted as Rainbow letting her fans give Sunset a crowd-surf.
 * In the short "Good Vibes," Sunset is seen breaking her shoes while getting out of work. Rainbow, in an act of ongoing kindness, offers Sunset some new shoes. (Bonus: Sunset is seen wearing similar shoes in "Game Stream.")
 * In the short "A Fine Line," Sunset is waiting in a line for a new video game titled "Tirek's Revenge." Rainbow joins her, and asks where the others are. Replying to this, Sunset says she didn't think the others would want to join her, possibly implying Rainbow is either the only one that really likes video games, or is the only one that Sunset thinks would be interested in the same interests as her. Rainbow then runs off and grabs the others, bringing Sunset's other friends back, and winking at her.
 * In both "My Past is not Today" and near the end of "Forgotten Friendship," Sunset's group of friends reach out to her, and in both scenes, Rainbow is the first to reach out. (In "My Past is not Today," it's by a frame, but in "Forgotten Friendship," it's undeniable that Rainbow reached out first.) Twilight is the second to reach out. Rainbow also winks in the "My Past is not Today" scene, and Sunset smiles at this.
 * In "Spring Breakdown," Rainbow goes out on a search for magic, and when Sunset realizes she might be in danger, she goes after the other.

Fanon
There hasn't been much SunsetDash content in the fandom, with the little content there is either including other pairings, being explicit, or has the duo drawn as horses.

Fandom

 * Sunset Shimmer/Rainbow Dash on FanFiction.Net
 * Sunset Shimmer/Rainbow Dash tag on AO3
 * Sunset Shimmer/Rainbow Dash on FimFiction.Net
 * Sunset Shimmer/Rainbow Dash (EG) on FimFiction.Net
 * Derpibooru Tag.
 * Tumblr searches for SunsetDash, RainbowShimmer
 * Fimfiction Group

Trivia

 * Rainbow Dash and Sunset Shimmer's colors compliment each other nicely, with Blue and Orange being complementary colors.
 * There is a boxed toy set with dress-able Sunset and Rainbow toys. There is also canon but edited screencaps of different scenes of the pair.