  Stationary black holes in 5-dimensional Einstein-Maxwell-Chern-Simons theory
possess surprising properties. When considering the Chern-Simons coefficient
$\lambda$ as a parameter, two critical values of $\lambda$ appear: the
supergravity value $\lambda_{\rm SG}=1$, and the value $\lambda=2$. At
$\lambda=1$, supersymmetric black holes with vanishing horizon angular
velocity, but finite angular momentum exist. As $\lambda$ increases beyond
$\lambda_{\rm SG}$ a rotational instability arises, and counterrotating black
holes appear, whose horizon rotates in the opposite sense to the angular
momentum. Thus supersymmetry is associated with the borderline between
stability and instability. At $\lambda=2$ rotating black holes with vanishing
angular momentum emerge. Beyond $\lambda=2$ black holes may possess a negative
horizon mass, while their total mass is positive. Charged rotating black holes
with vanishing gyromagnetic ratio appear, and black holes are no longer
uniquely characterized by their global charges.
