Bupropion
"I originally got it prescribed for depression. My doctor very casually mentioned that it would also help me quit smoking. I didn't think much of it except, "Yeah right... As long as it cures my depression." After 3 days of taking it, I didn't smoke a cigarette from 6:00 am to 3:00 pm (I usually smoked every 1 or 2 hours). By then, I realized that I hadn't smoked the whole time. I had completely forgotten that the medicine also reduced cigarette cravings. On the fourth day, I was only smoking 1/4 of what I usually did, and after I week I quit altogether."