Telecrapper 2000 to the rescue! This homebrew, open-source system hooks a computer up to a phone on an extension in your house. Based on caller ID (or lack of it) versus a user-specified black list, it determines when it should answer the phone for you.
It then goes through a scripted series of custom audio recordings, pausing after each one to allow the telemarketer to talk. The goal is to draw the hapless telemarketer into an endless incoherent conversation. The computer keeps a recording of both halves of the resultant call for your personal amusement.
Try the Is This Chris? conversation.
Or maybe the Rambling Grandpa will snare them!
How about the Hip Hurts sidetracking ploy? That recording even had a Flash version made for it.
Fun for the whole family!* You know you want one. (I sure do!)
Special thanks to rigelkitty for posting this gem.
* Except families containing telemarketers.