The logical answer of course is your employer. To say otherwise is to invite criticism that are you are being a smart aleck.
Changing the way you look at this whole idea of working for another may change your attitude about how you deal with work.
Think of it this way, you are running your own business, you are therefore working for yourself and you are your own product or service. What do your employers represent then, you may ask. They are your customers and in order for your business to flourish, you have to make them happy. Their happiness improves the market value of your product. Your ability to do more than expected makes your product attractive both to them and other potential customers. The more attractive you are, the more people will be interested to retain your services, hence the better job pricing offers.