I'm all about experimenting with different materials to get crazy effects... on some of my paintings I've added soap, water, household cleaners, cleansers, table salt, etc to see what happens. Lately - I've been using latex acrylic house paint because the technique I've been trying to accomplish needs the paint to be very loose and free, but not watered down and transparent. I've got a whole stock pile of different sizes of glass, wood and metal that I intend on using instead of canvas in the future as well....
I would be very interested in hearing all the crazy things people use to try and get different effects with their paintings...