When it comes to phone spam, my favorite thing was to give the phone to my 5-year-old. I'd say, "hold on" and then let my kid take over. She used to screech fake 'hold music' at the top of her lungs until they hung up. I also like to ask if they have accepted Jesus and offer my testimony. That kills off stock boiler room calls immediately.
There's a hilarious Youtube video of a comedian (Tom Mabe) just tearing a spam caller a new one by faking a murder investigation and threatening to embroil the caller in it for calling a freshly murdered guy. NSFW but funny as hell.
https://youtu.be/aOvXxnSEQKY
There was also some guy who used to get these scammers to send him photos of themselves with all sorts of ridiculous stuff written on placards they held up, to prove they were legitimate.