I've discovered that answering all their questions with magic 8 ball answers drives them insane, for example:
"HI! HOW WOULD YOU LIKE TO BUY FUJITSU AIR CONDIIONING FOR THE LOW, LOW PRICE OF $130 DOLLARS?"
"Better not tell you now."
"UHHH..UM..CAN I INTEREST YOU IN ONE OF OUR OTHER PRODUCTS?"
"As I see it, yes."
And so forth. I can keep a conversation for ten minutes, going round and round in circles until the telemarketer hangs up.
Bahaha! I should try that one sometime soon..1. Talk like a 3-year old. 2. Yell "some people eat bugs!" and hang up. 3. "HAY GUUUURLLLL"
I just answer and put the phone down, letting them talk until they realize I'm not listening and hang up.