Either Twilight or Rainbow Dash.
Twilight because she loves books.
Rainbow Dash because she's awesome and since a lot of things I do start with me or a friend saying "Let's do something stupid." I'd say she's the only one bar Pinkie that would join in. xD
I'm new to the herd. I actually only started watching MLP a few days back but better late than never, right? xD My favourite ponies are Rainbow Dash, Twilight and Fluttershy. :3