Small sign that used to hang on the wall of my school's library.
I always thought the sign was pretty silly since:

a) Well duh, of course any cigarette can be my last. Any cheese sandwich can be my last one too. And you don't see signs saying "be nice to golf players, any golf match can be their last", do you? What's the difference between golf players and smokers? We both enjoy what we're doing, can make nice salads at times and are considered social outcast by certain others.
How about "be good to non-smokers, any healthy speech can be their last"? I'm going to kill some of those !@#!@#-health addicts if they don't stop whining about my joyful attitude. I love to smoke, not to abuse small children. Stop picking on me!

b) Fine, so when you're convinced that all of us smokers are suddenly going to drop dead, then BE nice to us! No, this does not include puberal coughing, starting a speech about cancer, complaining about smokers' a-social attitude and certainly not calling me names cause I do not wish to smoke outside when it's raining.

I once tried to explain my concerns to the librarian. She stared at me with glazed eyes, then lit a cig herself. I should have known it from the liver spots on her hands and that strange cough she always had, she was one of us.
I now realize she'd just hang that sign there to show non-smokers' hypocrisy.

She passed away last summer at age 50-something, by the way. Lung cancer, I was told.