(A fun combination of two classic puzzles, hope seasoned puzzlers enjoy.)
Having escaped through almost all of a labyrinth, you are met by three magical doors. Two of them lead to certain and immediate death, and one leads to freedom. They are magical because which door leads to which changes every time a new person approaches.
However, there are two guards that guard these doors. One always lies and one always tells the truth. Due to the magical nature of the doors, they do not know which door leads to which outcome.
As you approach the three doors, the guards instruct you to pick a door. After you do this, the guards are given a flash of magical insight, and one of the doors (excluding potentially the one you picked) that leads to certain death is revealed to them. The guards then allow you to ask a single question, and pick one of the other doors if you wish.
With this one question, what is the best possible outcome you can achieve?
Edit - As some have identified, this is exploiting the same techniques as the Monty Hall problem (hence the name), the difference lies in the fact you do not know which is the dud door, and cannot simply ask the guards.