Brownian motion exhibiting absolute negative mobility
  We consider a single Brownian particle in a spatially symmetric, periodic system far from thermal equilibrium. This setup can be readily realized experimentally. Upon application of an external static force F, the average particle velocity is negative for F>0 and positive for F<0 (absolute negative mobility). 
Ralf Eichhorn, Peter Reimann, Peter H\"anggi (U Augsburg)