Credit Card Junkmail
This is one I like to scribble on a piece of scrap paper and enclose in the prepaid envelopes that credit card companies insist on sending me.

Dear CitiBank,

You are no doubt wondering why I've sent you a bunch of expired pizza coupons. Now you know how I feel when you send me a bunch of paper I didn't ask for an am not interested in. I will be doing this every time you send me a credit card application. It's my little contribution to raising your postage costs and discouraging you from sending junkmail.

I'm Adam Scott,
The last angry young man