Musician or Singer
Very few musicians or singers are in a position of power—most audition regularly and are at the mercy of recording studios, talent booking agents, etc. Some of those who break through are very powerful, but don't hang your hopes on being one of them. It's a long, hard road from Jenny from the Block to J-Lo.
The times you will feel most powerful is when you are actually singing or playing your instrument. Not only do you get to belt out or wail on those drums, but you have the power to move your audience emotionally. Just a heads-up—if they are moved to cover their ears with their hands, that is more of a physical response than an emotional one.