When I was 16 I became an "eBay trade assistant" - basically people who didn't know how to sell stuff on eBay would pay me a 15% commission to sell their stuff for them. The work was really trivial, but a lot of the people I sold stuff for were 70+ years old and had some great antiques. It was easy money for a 16-year-old.
One day a guy contacted me and said, "Hey, I have a GPS from my work that I don't need, and I want you to sell it for me." I looked up the GPS; it retailed at about $1500, and was selling for around $1,000 on eBay. I would literally copy/paste the official product description and earn $150 - a no-brainer. I told him to ship me the GPS.
A few days later, as my mom was about to take me to pick up my car from the mechanic, a FedEx guy came to our garage door. He asked if there was a "Scott Smith" that lived at our house (I don't remember the exact name). We said there wasn't. He said, "Oh, well I have a GPS here for Scott Smith." I said we were expecting a GPS, but that wasn't my name. My mom got nervous and turned down the package.
A few minutes later, as we were driving to the mechanic, my mom got pulled over by an unmarked car. It was a little strange to see an unmarked car in our small town, but oh well, my mom was speeding (as everybody always is in that town). I put my iPod headphones in and didn't think twice about it. The officer asked her to step out of the car (again, I didn't know enough to think twice). After about 10 minutes of them standing there and talking I finally pulled my headphones out and heard "stolen credit card" and "GPS" in the same sentence. I put together what had happened pretty quickly, and explained it to the officer. The officer made a circling motion in the air with his finger, and four of five other unmarked cars that had parked discreetly behind us on the street drove off in various directions.
Turns out I was being used as a "fence" for one of the largest credit card thieves in America, as he was testing the waters of using trade assistants to sell on eBay. My next-door-neighbor (and a good friend of the family), who was a police officer, later told me that they had been setting up this sting for weeks. He recognized the address as being close to him, but we lived next door to a trailer park that had been notorious for crime of all varieties, so he didn't realize it was actually our house they were targeting.
Turns out the FedEx guy was an undercover FBI agent, and they had a warrant to strip our house down to the studs if we had accepted the package. In the end, we just explained what happened, and I had to turn my beloved Hotmail account over to the FBI. They said they would have me testify in court if they ever caught the guy/girl responsible, and I've never heard anything. So either they never caught him/her or my testimony was unnecessary given the email transcripts.
My mom loved to tell that story to girls I brought home for the first time. In retrospect it was probably a good litmus test to know if they'd be able to put up with me.