Joker Versus Joker (The Batman)
The Batman animated series had a very different kind of style to the Joker, I thought. For one, he was more animalistic, and even seemed to have more combat prowess. I think it would be interesting to have these two variations of the madman run into each other.
I'm kind of drawing a blank on scenarios, but the setting will be an amalgam Gotham City, half from the comic, half from the television series.