Those are all great, I especially like the Ring Test, Xavier. Here's another. You'll need a coin or some small object, at house parties I tend to use bottle caps. Ask her to hold out her hand and hold the object in it with her palm open and tell her to close her hand over the object when you try to grab it. Do this twice. Both times she should successfully block you. Then ask her to hold her open palm, with the object in it, in front of her eyes with the top of the wrist touching her nose. Now tell her to try and close her palm when you try to grab it. You should be able to, because its more difficult to judge where your hand is coming from in this position. This one never fails to entertain.