I've been known to smoke cigarrettes from time to time, but one thing that really chafes my lungs [apart from nefarious toxins] are the people who casually flick their butts all over the place. Litter in general just berates me, and living in a college environment, I come across hundreds of spent butts littering every entryway to every campus building.
Now, I realize smoking is bad and I probably shouldn't do it, but I refine my habits to best suit the general public. It's just courtesy. I never litter the ground with cigarrette butts, I'll look for an ash tray or other recepticle and if one isn't around, I'll carry my butt around until I find one.
Though it does get kinda frustrating at the end of the night when I sometimes remove upwards of a dozen used cigarrettes from various pockets on my person. Eww. At least I'm littering on myself and not on mother nature.
[Something of note: I smoke less than one cigarrette a day, these days.]