Varenicline
"Champix worked like a damn!!
I was three packs a day. Moderate COPD!
Tried many many times to quit; tried gum - made me sick; tried patches - kept me awake and made me nauseous. 
It took three pkgs but Champix finally worked!! (spelled champTix in US)
BUT; and I'm telling everybody this; 
the worst side effect is nausea and it was fairly bad. SOLUTION; buy a packet of gravol (or its generic copy) and take the champix tab WITH a gravol. It ended my nausea and I had no other side effects. My biggest thanks to all those fine folks who developed this drug. It worked really really well for me.
Good luck,
Jack in Vancouver."