In my circle of friends, this one is well-known by now, but maybe you haven't heard of it already:
You walk along a path until you reach a crotch. One way leads to your destination, the other to sudden death, but you don't know which one is right. Fortunately, there is a house with three dwarfs. One always tells the truth (A), one always lies (B), and one sometimes tells the truth and sometimes lies (C).
How do you find out the right path with only two questions?