If I don't recognize the number on caller ID, I usually don't answer it, but I wanted to screw with this obvious telemarketer. Not feeling overly ambitious, I picked up the line and didn't say anything. You can hear the "bunch of people in a room" sounds faintly in the background. And I heard breathing. After about 10-12 seconds I hear a sigh and the line goes click.
Other tricks I have used to screw with these jerks:
Talk gibberish. Make up a fake language. I did that one time and the person goes "Is there anyone there that speaks English?" I said (with a foreign accent) "Yes." .......<and waited>....... And they go "Well can I talk to them?" And I said "Yes, I English berry good, yes"
"Can you make decisions regarding the electric bill?"
"Yes, I English berry good, yes"
This only went on for a minute or two, but it was fun while it lasted.
My advice is don't get mad, get even. Have fun with it.
My mother in law blows a coach's whistle into the phone whenever they call her. One of those obnoxious air horns works well too. I say try to keep them on the phone as long as you can. Lead them on, let them think you're gonna buy what they're selling and then right at the end go, "You know what, I changed my mind. Bye" and hang up. That really pisses them off. Try to pick a fight with them. Call them names, etc. When they complain about it, tell them "If you don't like my attitude, QUIT CALLING ME"
Don't get mad, get even and have fun. Like this guy does:
http://www.tommabe.com/