Never have. I've considered it, but not for long.
I've seen drugs destroy too many family members. One grandma of mine is in the hospital with lung cancer, my aunts have it (still smoke, but they try and balance it out with good diet and exercise), another grandma has a lung infection and still smokes (the house stinks like hell), and my dad's been to jail too much for drugs. My stepdad's a pill popper, and seeing him high and later depressed and high just destroyed me. It's funny for a while, but the funniness wears off.
It'll stunt my growth, I'm still in high school. I've seen way too many kids pick up drug habits (13-year-old alcoholic and smoker? not fun). I don't want to die soon.
I've considered weed for when I'm much older, although probably not smoking it. Might not at all.
I don't mind when other people do. I'm opposed to it, but it's their life.