Burn After Reading
I found this an excellent Coen Brothers comedy with a large, excellent ensemble cast. It mixes middle-age infidelity with government politics and physical exercise. The core of the film is a kind of slapstick comedy of mistaken identities but there is a dark slightly cruel undertow to the whole thing.
All of the turns are excellent and while the plot might be a little lightweight it is really a peg to hang a cast of fools.