h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I was on Wellbutrin for about 3 months last year, even though I do not suffer from any form of depression.

In South Africa the drug is marketed as 'Zyban', and apart from being a powerful anti-depressant, it's also a remarkable aid to stopping smoking.

This is one of the side effects of the drug that the manufacturers have no explanation for. After taking Zyban for a week, I completely lost the urge to smoke. Nothing. It is as if the drug masked my body's dependency on Nicotene (I was at that stage an incredibly heavy chain smoker, and my doctor prescribed Zyban as a 'last ditch' resort)

I managed to remain smoke free for 6 months after finishing with the course of medication.

Strangely enough, South African pharmaceutical companies are marketing the drug as a stop-smoking aid rather than an anti-depressant.
Before anyone reading this tries to get hold of some of it to aid in stopping their habit, it is good to keep in mind that even in the absence of any depression the side effects are still quite noticable (Insomnia, violent outbursts, dissociation)

Speak to a doctor before doing anything :P