When your "target" is in the shower and you open the shower curtain and let a fart loose into the shower. Then you close the shower curtain and lock the "target" in with the stench. Extra effect if you can let a silent fart go instead of making it known that you were there. The heat of the shower makes the smell much worse.
Man, Julie was in the shower today and I shot in a Muslim Heat Seeker and she about hit the floor from the smell.