There is always the tried and true pick an obscure, lesser known or possibly even esoteric [1] language and talk about how it is different and maybe why it is different and what (if any) reasons someone might want to learn it in depth or actually try to use it for a project.
Or possibly more usefully you could try an intro to a deep concept in programming languages that people don't well understand. The classics there are things like "What is a Monad? Guess what, here's how you are using them already in C# or JavaScript...".
Or possibly more usefully you could try an intro to a deep concept in programming languages that people don't well understand. The classics there are things like "What is a Monad? Guess what, here's how you are using them already in C# or JavaScript...".
[1] http://esolangs.org/wiki/Main_Page