I know that I am a bit late to the party, and that this may have been address in the previous 59 pages, but I wanted to get my two bits in here.
So at my joint birthday party with a pagasister, we were outside away from the party and she asked me what my cutie mark would be. She had no idea what her cutie mark would be! It kind of freaked her out that were were as old as we were and would be blank flanks. That's when I told her my overarching theory on that:
We do not live in Equestria. While it may be nice to live in a world where, at the age of about 10, we would know what we wanted to do with our lives and have a singular focus, we do not live in that world. We live in a world where, at any given time, we can change our cutie mark to whatever we want. Unlike Equestria, we can change our destiny at the drop of a hat and go achieve what we ant in life. Think about what your life was like before you started watching MLP... now think about how your cutie mark may have changed after that experience. That's the belefit of this world over Equestria... we can fight the future. There is no set path to walk and nothing you need to be, except yourself. Tomorrow has unlimited possabilities. Go learn a new langage, or learn to bake, or drive a manual transmition. You can get passionate about anything and still discover what is right for you!
With all that said, I would have a pair of Ice Hockey sticks as a cutie mark, becuase Ice Hockey is awesome.