To acquaintances and strangers - Fluttershy. I generally keep to myself and help others if they need it.
To pals, friends, and family - Pinkie Pie and Rainbow Dash. Funny, random, ambitious (taking over the world is a hard goal) and loyal to my friends.
When I'm by myself - Applejack and Twilight Sparkle. Sometimes (and when I'm in solitude), I wear my game face and devote my time into improving myself- physically, mentally, and musically. I take a few minutes once in a while to contemplate about my morals and if I live up to them.
Does that make sense?