I actually get excited when I get telemarketers because the robot sometimes fools them enough to keep them on the line for a few minutes. The longer the conversation, the more irritated the telemarketers get, and that's quite satisfying. Here's some sample calls:
I've gotten some of them irritated, not on purpose, but it ended up them being quite angr, yelling new and interesting expletives I had never heard before, I took it as an enriching cultural exchange with country all the way across the globe. But then I started to wonder if they'd just go and add my number to some "please call me" database in revenge.
A good example is when roofers or other construction (generally using the "we will be in your neighborhood anyway..." scam) company calls. Just reply, "give me your contractor's license # so I can look you up."
Seems like the recording is fixed? Lenny is great because the script actually waits for the marketer to finish speaking, making it more believable and stretching the call further :)