Rainbow Dash. Her tenacity and confidence in getting thing's done is unparalleled in Ponyville!
...Then again, Pinkie Pie is the reason I've laughed through most of the series so far, and her naive, always upbeat innocence is just too cute!
And speaking of cute, Apple Bloom is almost at the very pinnacle of all thing's adorable! I mean, could you turn down something with this expression?
Buuuut, her big sister, Apple Jack, is a kindhearted, determined, tough cookie to crack! And a darn good apple bucker to boot! A little stubborn, but her heart is always in the right place.
But magic and intelligence have never made as harmonious of a mix as Twilight, so she too is a close first.
However, Spike's friendly demeanor and on-the-spot wit also makes for a wonderful partner to Twi, and even better all around character!
I... I don't know which to pick, honestly.