Nose-tap seemed obvious, but I never thought of forehead-tap or chin-tap. (I dismiss the "usual" way ... covering the screen with my other hand.) I'll add those to my repertoire, thanks!
A knuckle tap is a good one too. Works well when fingertips are covered in BBQ sauce, grease, etc...
Knuckle tap and scroll are common among smartphone users.
Oh I almost forgot, you might like my preferred way of dismissing Apple Watch / Android Wear: I call it the "Karate Chop". The surface area of the outer edge of your hand is enough to cover the screen :)