For us, missionary is not only one of our least favorite, its also the position that is seldom done...not counting obscure Karma Sutra type yoga positioning of course. 🙂
I would be lying if I said doggy-style was our most often done position, its our favorite, but with 4 young children in the house, sex for us is mostly quickies when we can steal away to the bedroom, therefore most of the time it is my wife on top of me.