Poisson structures on ℝ 2 N having only two symplectic leaves: the origin and the rest S. Zakrzewski (2000) Banach Center Publications Examples of Poisson structures with isolated non-symplectic points are constructed from classical r-matrices.
Potentials unbounded below. Curtright, Thomas (2011) SIGMA. Symmetry, Integrability and Geometry: Methods and Applications [electronic only]