Our first will be Rainbow Dash, not because best pone but because probably most popular. This uses Edges and information from my My Little Pony: Friendship is Magic conversion.
Name: Rainbow Dash
Race: Pegasus (Abilities listed below)
Cutie Mark: Rainbow Lightning
Experience: 100 (Legendary)
Agility d10; Smarts d6; Spirit d8; Strength d8; Vigor d8
Pace 8; Parry 6; Charisma –1; Toughness 5
Flight Pace 12; Climb 2
Hindrances: No Hands, Size –1,
Edges: Flight, Cloudwalker, Sonic Rainboom, Fleet-Footed, Dazzling Display, Weather Touch, Dodge, Combat Reflexes, Manipulate Weather, Arrow Flight, Killer Instinct, Brawler, Common Bond, Top Gun
Skills: Fighting d8, Intimidation d8, Notice d8, Stealth d6, Taunt d8, Throwing d6
So all ponies begin with Size –1 and the No Hands Hindrance (being that they, in fact, have no hands), but can use their tails and mouths to generally manipulate things. They also begin with a Cutie Mark, which provides either a +2 bonus to relevant skills once per session, or a free Edge that ignores all requirements. In addition, pegasi also begin with the Flight ability (Pace 6" and Climb 0) and Cloudwalker, which allows pegasi to interact with cloud material as though it were solid.
Rainbow Dash in particular has traded out her Cutie Mark Edge to instead have access to Sonic Rainbooms at character creation. In addition, she took Fleet (with an additional Minor Hindrance for both her ground and air speed) and Dazzling Display (+1 to Test of Wills rolls and a crazy contrail when you fly).
Dash is one of the greatest fliers in Equestria, and one of the only known individuals in the world that can perform a Sonic Rainboom maneuver. She has a strong sense of will and a very close connection to her friends. She is also highly competative and hates losing.
As captain of the Ponyville Weather Team, she is a master at manipulating clouds, living in a personal cloud house just outside the town. Arrow Flight, Weather Touch, Manipulate Weather, and Top Gun are Edges that let Rainbow Dash pile on the speed and keep control over the skies, and Doubt necessitates that a Spirit roll must be made to Benny any Agility rolls. This was bought off fairly quickly.
So there's Equestria's weather captain in ten seconds flat. Leave comments and questions below.