Rainbow Dash

Rainbow Dash is a high-flying athletic Pegasus from Cloudsdale and the holder of the Element of Loyalty. She loves to fly, race, pull off daring aerial tricks, and generally do everything fast and awesomely. She makes a living as a Weather Pony, managing the weather around areas like Ponyville. Despite living in the clouds, she's seen around Ponyville just as often as any of the others.

Move List
As of her clash with Applejack in Chapter 8, it appears her moveset takes cues from Sonic the Hedgehog in Super Smash Bros. Brawl.

Back-story
Rainbow Dash grew up in the rough-and-tumble (yet soft and pillowy) streets of Cloudsdale, where she had to constantly prove herself in the face of mockery from all the surly colts who enjoyed bullying others. One day, she came upon Hoops and Billy giving Fluttershy a hard time and wouldn't have any of it. Rainbow Dash accepted the bullies' challenge to a race "for Fluttershy's honor." Fluttershy was quickly taken from the scene, but Rainbow Dash found herself enjoying the race and the free feeling of going so fast. When Hoops pushed her, Rainbow Dash responded by speeding past him effortlessly. She crossed the final goal and turned on a dime, the speed causing her to break the sound barrier and cause a Sonic Rainboom. She realized her love for speed and competition and earned her Cutie Mark because of it. That Sonic Rainboom is the same one that caused all of the rest of the Mane Six to earn their own Cutie Marks as well. Since then, Rainbow Dash has dedicated her life to being fast and cool. In fact, she quit flight school in order to live her life her own way. She idolizes the aerial performance group The Wonderbolts and pines for an opportunity to join their ranks. In the meanwhile, she spends her time trying to be as awesome as possible.

Personality
Rainbow Dash knows that she is awesome and spares no words or actions acting upon it. She carries herself with a confident swagger that is often backed up by genuinely impressive acts. She is also just as quick to go overboard with her confidence straight into arrogance. When showing off or basking in her own self-worth, she tends to forget about the world around her and act callously. For the most part, nobody makes a big deal about this since they're used to it from her. Being so amazing even makes Rainbow Dash act lazy or even sincerely be lazy. Since she can be up and productive in a self-professed "ten seconds flat," she is rarely confronted. Behind the confidence, there lies an insecure pegasus. She can talk a good game on a normal day, but she takes to pressure very poorly, especially when the Wonderbolts are involved. Being faced with a real opportunity gives Rainbow Dash temporary but vicious performance anxiety. Despite the callousness, Rainbow Dash does live up to her Element of Loyalty by having the well-being of others in mind. She has a funny way of dealing with sensitive situations, but she's there to do what's necessary, especially if it involves going fast or doing something cool.

Abilities
Rainbow Dash may just be one of the fastest fliers in all of Equestria. She is able to reach and maintain high speeds and even fly fast enough to break the sound barrier. She is also agile enough to turn at a complete 90 degree angle when breaking the sound barrier and make sharp turns without any loss in speed. In addition to all these, she has considerable strength, being able to best Applejack at forehoof wrestling, and even had the time and skill to become a Black Belt (or at least rent one).

Campaign
When she heard about the Cutie Mark Clash, Rainbow Dash was the most enthusiastic and even the first to sign up. Her primary motivation was her natural sense of competition, but she quickly found out about a generous cash prize to the winner. The cash was an added incentive, but not a deal-maker since she was only amazed at the larger number.

That was before she was introduced to Gil. Gil approached Rainbow Dash, having heard about her performing the Sonic Rainboom. Telling her about him own Sonic Boom attack, he expressed anticipation at clashing with her eventually to compare the attacks. This flared up the competitive spirit in Rainbow Dash and caused her to declare him a rival.

Before the proper start of the tournament, she managed to talk Fluttershy into helping her practice translating her acrobatic moves into fighting moves. While taking Fluttershy to scout Gil, Rainbow Dash ran into her old enemies from Cloudsdale, Hoops and Billy. The bullies challenged both of the Mane Six pegasi to a fight where Rainbow Dash revealed that she was trying to get Fluttershy as a fully fledged partner. Rainbow Dash begged plenty before Fluttershy agreed to at least not run away. When Rainbow Dash called out the name of a trick, Fluttershy snapped to attention. The two managed to pull very effective teamwork and win the fight. Their condition after the fight forced them to spend some time in a medical tent, at least in the opinion of Hayley.

Some time after that the two parted and Rainbow Dash found herself alone and looking for a fight. She lied to Applejack, telling her that she knew where her sister was, just to get a fight. Her gambit ended up a bust as Applejack won the fight. Revealing the lie made Applejack furious, to which Rainbow Dash replied by demanding what the Earth pony's real problem was. She listened patiently to Applejack's issues with her brother and herself, giving Applejack some reassurance. The two parted amicably and Rainbow Dash is currently left at that.