Who Am I?

My brother's Halloween/10th Anniversary with Tim celebration comes up on Saturday.  What to wear?  What.  To.  Wear?  The bloody screwdriver sticking out of my cheeks?  The bloody knife sticking out of my neck?  I've done that so many years in a row.  Such fun scaring the sh*t out of the young'ns at the front door.  But you know how I hate to repeat myself.  This year, for the party and the impressionable trick-or-treaters, I'm going classy.  No blood, no gore.  This year, I'm aiming for a whole other kind of spooky.  I've placed my order and while I await the arrival of my haunted apparel, I'm going to give you a few hints:  I want to use my position to help others.  I've volunteered as a sales clerk at a department store.  I have plans to start my own fashion label.  In 2010, I competed in a marathon.  Who am I?