Human Antenna by 808 Magic and Alan Wong

This one's a bit of a classic in the sight gag department: the Human Antenna. Despite the fancy name, it's just a couple of retractable metal antennas with sucker cups. You stick one on your forehead, one on your spectator's, and suddenly you're a mind reader. Or at least it looks like it. Great for a comedy mentalism bit when you're not taking yourself too seriously.

No batteries needed, which is lucky because I'm not sure where you'd hide them anyway. It's all about having a laugh, with a dash of magic to keep things interesting. Though honestly, it might just be more about the laughs. You decide.