There was one I did have fun making:

Back around 2007 it was about AI, and for part of it I'd memorized like 2-3 minutes of what I was going to say, along with careful timing. The plan was that I'd start wandering around, including around the back of my laptop so I wasn't looking at the projector or laptop screen - and during that time, robot characters would wander onto the screen and start running around. The idea was I wouldn't look back until right after they hid themselves. I think I'd even put a spot in the middle where I could glance back while they were hidden, then they'd come back out.

I don't remember why, but I never got to present it.