I'm in love with shaving creme right now. There is so much you can do with it: squirt it on the table and let the kids play (bonus - all that glue and grime will clean right off too); mix it with tempura paint and freeze it, it feels great!; try mixing it with finger paint, adding a popsicle stick and freezing it in small yogurt containers - instant ice painting; mix it with glue and create puffy art; want some snow? no problem. just mix together shaving creme and baking soda.
Oh, and you can also use it to shave. But that's not nearly as much fun!