When I'm in the mood I'll troll the obvious phone scammers, especially and always anyone claiming to be calling from Microsoft about a problem with my computer.
Why do I do that? because I don't use Microsoft systems, so anyone pretending they're "helping me" deserves having the tables turned on them.
It's a good game to see how long you can waste their time, because the longer you do, the less they're scamming someone who isn't quite so IT savvy. My favourite line is to put them on squawk so they can hear me typing, and just carry on working, they assume the typing is me following their instructions.
I always ask questions that aren't in their script, like "How much do you charge for computer support?", or pretend I've accidentally hit the reset button to reboot the PC, or there's someone at the door, (I go and make a myself a coffee) and they nearly always wait... and I then play along until they ask me to click some link or enter a URL, at which point I tell them I can't do that because I'm a computer engineer, know what their scam is and love wasting their time...
The reactions I get have varied from them slamming the handset down so hard they probably broke it (many times), angry questioning (a couple of times), one guy exploded into his native Asian tongue for a four or five minute long tirade of abuse that would have made even me blush if only I had understood what he was saying, and one had his supervisor phone me back and threatened that he'd call the police for wasting his employee's time!
I told that last one that I'd look forward to hearing from the police as what they were doing was far more illegal than what I was doing.
ps. yes, I am on TPS, but it has no effect for the international scammers.