Zyban (also called wellbutrin) was very effective for me. I used it in conjuction with smokeless tobacco. After I hadn't had a cig in a couple weeks I started cutting down on the dip by mixing it half and half with "herbal" (tobacco free) dip, which is basically just flavored grass. After a couple weeks of this I cut it to 75/25 and then cut the percentage in half again, and finally switched to "herbal" altogether. After a couple weeks of that I switched to gum.
I haven't had a smoke in 14 months & have been completely tobacco free for 12 months now.
My insurance company wasn't going to pay for the Zyban for smoking cessation, but my doctor didn't write what it was for on the prescription (it's also used to treat depression), so the insurance company just assumed it was for that and paid it.