So you know that it is just a person trying to make a living...but fuck [them]. Bad karma there.

If it is a number I don't know, I just answer, listen to the short pitch (usually 20-30 seconds). Say, nicely "Thanks, but I'm not interested. Have a nice day" and hang up.

I don't waste my time with some passive-aggressive bullshit. If you answer and are polite - these are just people trying to make a living, remember? - while making clear you aren't buying, then they'll take you off their calling list. Problem solved.

Choosing to be a passive-aggressive dick says more about you than the sales person calling you.