Ferry dock @ Billy Bishop Toronto City Centre Airport

The airport closes some time around 11:00 pm (no takeoffs or landings allowed except medevac) and the ferry across the channel stops, so unless you can track down a water taxi you're stuck for the night. A few years ago I talked to one pilot who landed late, didn't get away in time, and ended up sleeping in his plane.

The new ferry is free, at least so far. If you fly in with four people, that's a significant saving at $5.50/person.