My brother and I used to mess with telemarketers all the time. get the dog riled up, and get her to start barking, and then hold the phone by her, that kind of thing.
Best one I think was when I got a call from a telemarketer, and I told him that I needed to get the other extension, and set the phone down. About a half hour later, my mom picked up the phone that was off the hook, and the telemarketer was still there!!
