I love taking advantage of that whole "where's my phone" panic.
Say we go grab a beer after work. I'll take a picture of your phone when you go to the restroom, and then after you go home, I'll send you a text with the picture of your phone saying "you forgot your phone." People seem to forget they've received that text...on their phone.
Another one i did once was after meeting my gf for lunch, she had school and i had work. We're side-by-side at a red light, so i call her and ask if she knows where she put her phone. And i watched through the window as she proceeded her tear her car to ribbons as she can't find her phone in her car. My giggles are what gave the game away.
