What a nice thing to do... send spammers this sticker to let them know how much you appreciate them sending you spam, oh, and to let them know you've blocked them.

Full text:
"Thanks for your spam.
To show my appreciation
I've blocked you.

Have a nice day :-)"

I do not earn any credits from sales of this sticker as to keep the price as low as possible and make it cheaper to send it to spammers.