I'm nice to them, out of sympathy, but still have fun. When they call and ask for the lady of the house, I say "I am the lady of the house." (I sing down to low E if that's a clue to the joke...) ;-)

Some are on machines that pick up the first "pick-up" so often at work I answer and there's no one there, because some other sucker answered faster than I. Since then, I used to use the Ma Bell rule of no call gets more than two rings, now I use my own, every call gets at least two rings.

I've also have very good response to being polite and saying the magic words... "Take me off your call list and don't call me again." But I had one guy call back and thought his accent and pitch were to some huge firm, where I wouldn't recognize him. I told him I already asked him to stop calling, last week, and he called me some rude names and hung up. I wish I had been recording, this drip would have made a good joke sound bite.