Say, "This phone line is for emergency use only. Do you have an emergency?"
If they say "Yes" to emergency line say, "Please state the nature of the emergency." Then insist that their emergency isn't an emergency. Hang up.
If they say "No" to emergency line say, "I'm sorry but this line is for emergencies only." Hang up.
Pretend that you are a hostage negotiator, and try to get the telemarketer to release the hostages.
Order a large pepperoni pizza, some garlic bread, and a meatball sub.
Pretend that your phone line is an automatic phone sex line.
Repeatedly dial the phone. Mutter that it isn't ringing.
Say, "Oh no! It's the Feds! They're on to us!"
Speak a foreign language.
If you do speak a foreign language and the telemarketer gets a person who speaks the language you used, speak another language, use a made up language, or say that you were speaking English the whole time.
Pretend that the telemarketer is your husband/wife or boyfriend/girlfriend. Talk sexually, making references to what you are going to do to him/her later tonight. When you "realize" that you are not speaking to your husband/wife/boyfriend/girlfriend yell, "Pervert!" Slam the phone down to hang up.
Say, "Help! I'm being robbed! He's got a gun!"
Try to sell the telemarketer something.
Ask him/her if he/she can smell bacon. Insist that there is a strong scent of bacon over the phone.
Pretend to be an escaped mental patient. Mutter things like, "They'll never catch me again," "No! Not the jacket! No, no, no!" After saying one of these mutter incoherently.
Make him/her dance for a sale. Claim that you won't buy because you couldn't see him/her dance.
Make him/her sing to get a sale.
Engage him/her in an "intellectual" conversation on an extremely boring subject.
Say, "I told you. I don't know where your dog is!" Then hang up.
Pretend you are a telemarketer from a rival company. Get him/her to buy your product.