In the past when I would get a call from a telemarketer (I think they put me on their own "do not call" list since I haven't had a call in years), and I felt like taking a break, I'd answer....
There are so many things you can do.
If they say they "will save you money" and its something that you aren't paying for now, ask when they will be sending you a check. Become irate and demand to talk to a supervisor when they say they aren't sending you a check. Go as high up as you can, demanding the check for your promised savings....
Immediately tell them you are really glad they called because you need to sell just one more life insurance policy to make your quota, and start in on the hard sell....
Ask if the caller is wearing a tinfoil hat. If not, refuse to speak with them because (fill in the blank; aliens, your third grade teacher, the government of Berundi, whatever) will be able to hear you by reading their brain. Tell them to call back when they are properly shielded, and to use a secure line.
Pretend you speak only Polish, or some other language. You don't have to actually speak any other languages. Just make up nonsense words, and string them together and make it sound like questions.
Try, with great sincerity, to convert them to some religion that you just made up.
Sell them a '53 Buick.
Make them give the proper password before you can speak to them.
Ask what they are wearing. No, under that.
Interrupt every few seconds with some random, unrelated subject.
Ask if you can put them on hold for a second. Then put the phone down and see how long they are willing to wait.
Pretend that you called them and keep asking for (make up a name). Insist that they get that person on the phone right now.
Its limited only by your imagination. (The ones where I demanded they send me a check never called again. Most of the others didn't either.)
