Answer: Clearly it's Rarity.
Explanation: We can all agree that Twilight is a real overthinker and just annoying at times, Rainbow dash is pretty cool, but she sometimes creates conflic that just doesnt have to be there. AppleJack is pretty decent but she doesnt play a big role in the show as much as she should. Fluttershy goes for the same with AppleJack, she is either talking to animals or just not there. PinkyPie is pretty enjoyable and keeps the situation positive, either than that, thats all she does. Rarity on the other hand, is pretty much always there and tries to make it all about her....in some cases. She makes everything into fashion and is serious at times as well. She is nice and has a fun personality!