It'd be fun to put the Mane Six as playable characters in a game and have them all play very differently.
I'd rationalize Pinkie's inexplicable skill at popping up in wierd places as part of her form of parkour which focuses on creative mobility, rewarding you for getting her to jump from point A to point B and then finding the narrow crawlspace into a good hiding place. She'd be a tad like a party ninja, sneaking around to give cheerful surprise parties :3
Twi would be relatively less-fit and mainly focused on her spellcasting, but have her massive magic power balanced by low stamina, so you can only cast so much magic before she has to stop and rest.
AJ would be less quick, but have steady balance and some wicked lassoo moves and powerful jumps and melee. She'd have lots of grapples and lassoo restraint moves, and powerful kicks.
Dashie would be all about her flight and quick movement, with very fast acceleration in the air. Her style of play rewards thinking like Sonic or Tails or Knuckles with a healthy does of Parkour, and she'd totally have a scoring system for doing stunts :3
Rarity would have an intense focus on crafting skills, disguises, and lots of social-fu, with witty dialogue everywhere from her. Her melee game is more martial arts than anypony else besides Dashie and AJ.
Fluttershy has some great grapples and submission holds (lol), and she'd have the Stare for self-defense. A big part of her playstyle is persuading her animal friends to support her here and there :3