My dad had to do something like this in order to teach people to give good presentations. He did his on taking on the three peaks walk and it went down very well despite the actual subject not being overly interesting.
He worked humour into his though so I suppose unless your confident in your abilities to amuse people it may not be suitable considering your aim is to actually get the job
Oh, I know, talk about how they're all an illusion because it's all in your head and none of them really exist because you made them up. That should creep them out- my old maths teacher used to do it to us.
Why don't you do something which is of great interest to you? . . .ie hobby . .
When I had this same sorta thing at college many moons ago, I did my presentation on Dancing, as that means a lot to me, ie hobby since I was 4 years old.
I found doing this, I was comfortable talking to my audience and I knew what I was talking about. I also bought in my Pointe shoes as a visaul aid as the people in my class had never seen a pair of Pointe shoes, really did get the class gripped on what I was talking about.