Every known (or maybe even conceivable) system of classical mechanics can be cast in the form of symplectic geometry.
Poisson after whom the bracket that introduces the symplectic structure on phase space is named, died in 1840. Through Hamiltons recasting of the equations of motion as the flow of a vectorfield induced by an observable and a symplectic structure, through the Noether theorems, Heisenbergs quantization, Diracs cannonical analysis of gauge systems to todays work on the interpretation of Quantum Gravity, symplectic structures have provided the foundation (sometimes implicitly) of almost the entire apparatus of mechanics for the last century and a half at least.