Some witch-doctors have been known to poison people with Fugu or pufferfish venom. It's extremely deadly, but a precisely controlled dose can put somebody into such a deep coma that laypeople will think they are dead. The witchdoctors then steal the 'bodies' from the morgue, administer an antidote, and then have an 'undead' person to either keep as a servant, or to show off and intimidate others with their skill. One Haitian black magician claims that he's successfully done this to several people, but that his attempts killed many.

Of course, these people aren't really zombies, since they're never dead in the first place - merely heavily comatose.