I usually try to put some twist on their call to give them a hard time.
Hello, we're selling light bulbs to raise money for....
Please (sob), oh my god (sob), I can't believe this...
Sir?
You sell light bulbs?
Yes sir, we're raising money for..
Please stop, for the love of god, please!
Excuse me?
You have wonderful timing. I just got back from the optometrist and he confirmed I have cornea cancer and I'm going to lose both eyes. SO WHY IN THE FUCK WOULD I NEED LIGHT BULBS WHEN IM GOING FUCKING BLIND!!!!
....click...
Betcha she remembers that call for a long time.
I have other riffs, based on what their selling. I love telling anyone selling me home improvements about my pending divorce (it's a big lie), and what that bitch has put me through, and SHE'S getting the GOD DAMNED house so call HER not ME!!!
Hee hee, I love it. 
There's only two kinds of cigars, the kind you like and the kind you don't.
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