Bupropion
"I took Wellbutrin several years ago and after about two-three weeks one day I noticed it had been 6 hours since I had even thought of a smoke. I get down to about 2 cigs a day (usually one in the am and one after dinner) so I thought well 1or two a day isn't going to hurt me but it doesn't work that way you gradually go back to the old habits. My advise is that moment when you get to the point, put them down right then. Don't be fooled it will come back if you don't stop then. So, I went back to my 2 pack a day habit and my Mother recently died from lung cancer (also a smoker).  I have gotten back on the wellbutrin as of yesterday and hope it works as well for me this time."