Nanoelectromechanical systems (NEMS) are devices integrating electrical and mechanical functionality on the nanoscale. Because of individual electron tunneling, such systems can show rich self-induced, highly nonlinear dynamics. We show theoretically that rotor shuttles, fundamental NEMS without intrinsic frequencies, are able to rectify an oscillatory bias voltage over a wide range of external parameters in a highly controlled manner, even if subject to the stochastic nature of electron tunneling and thermal noise. Supplemented by a simple analytic model, we identify different operational modes of charge rectification. Intriguingly, the direction of the current depends sensitively on the external parameters.