Another funny one
One that I've tried and is fun is to use a foreign language. If someone without a Latin accent calls, I have said, "No hablo Ingles.", there is usually a delay and then the solicitor starts talking again and I repeat the Spanish phrase and they will hang up. If the solicitor sounds Spanish, I use Germnan, "Bitte, Sprechen sie Deutch" or "Ich spreche kein English."
I've only done this a few times to Scientologists because I screen all calls and do not take Org calls. However, a few times, someone tells me they will call me at a specific time or someone I am speaking to may say they have to handle something and will call back in 5 minutes. When the phone rings at the appopriate time, I pick up without screening and if the Call is from Scientology or any other solicitor I use the foreign language. If the person also speaks the foreign language, they usually ask, "Is this Lakey?" and I say, "I'm sorry, you have the wrong number." and hang up. They then redial within a few seconds but I don't answer and let it go to voicemail.
Its a good system and works well for all situations. The one I like most from the other suggestions given is to give the phone to a little kid, also Dull Old Fart has a great idea about setting up a tape.
Lkwdblds aka Lakey