I recently picked up some Crayola window markers on sale (40% off). I paid about $4 for the set...BARGAIN!! We tried them out on a mirror and a window, but they were really hard to photograph! They work really well, especially on the mirror. I encouraged R to draw his face in the mirror, discussing the parts of his face and how many eyes, noses etc.
We also tried them out on alfoil. This also worked will, and R really enjoyed the noise that the markers made on the foil. He draw really fast to make more noise.
We will be using these markers a lot more!