I tell the students in my topology class that we will have an aural final exam, or is it 'oral'? Both seem appropriate, but I'll go with 'aural'.

The students don't know what an aural exam entails, nor do I really, but it makes them happy anyways. I think I'll just set a normal exam, but instead of giving them the questions on a sheet of paper, I will shout them at them.

If it goes well, next semester I will try a rural exam.