Imagine a device with a little seat, a large propeller, and huge rotors. A small counterotor in the back retains the balance. Sitting in the seat and violently pedaling, the user could lift himself aloft.
...eeeexcept that the rotors would have to be about 30 feet across, and one would have to pedal really really hard. It'd have to be made of the lightest carbon fiber, and even then it probably wouldn't work.