Another interesting Hamilitonian system is the three-particle Toda lattice. This system describes three particles moving on a ring with exponential interactions. If the particle masses are all the same, the system is integrable and both first integrals are known analytically. One is the total energy and the other is a fairly complicated quantity that reduces to the angular momentum in the limit of small displacements. If the masses are unequal, chaos can appear. This system is described in Chapter 4 of "Chaos and Integrability in Nonlinear Dynamics" by Michael Tabor.
The double pendulum system is one of my favorites. It is simple to write down the equations, easy to build, and provides rich chaotic dynamics that are easy to visualize.
Interestingly, the double pendulum equations are mathematically very similar to the three-body problem, where the trajectories are largely mediated by rank-1 saddle points.
Apart from double pendulum system and reversed pendulum, I recommend you the papers of dr. Ch. Skokos about chaos detection tools like SALI and GALI. One of the used models is a N-dimensional Hamiltonian, called Fermi - Pasta - Ulam lattice.
I attach one of my papers about double pendulum and a lesser known indicator of order and chaos, called Fast Norm Vector Indicator.