I know that a lot of people like Mexican vanilla. It's cheap and flavorful but the flavoring is not vanilla and is actually banned in the US. From the FDA-
"Tourists tempted to pick up bargains south of the border should beware of one bargain that isn't a good buy—a so-called “vanilla” flavoring or extract that isn’t vanilla flavoring or extract at all, but instead is made from a completely different plant material that contains coumarin. Coumarin is a substance with potential toxic side effects banned from food in the United States.
This flavoring product may smell like vanilla extract, taste like vanilla extract, and be offered at a cheap price, but it could present a significant risk to some people’s health.
Pure vanilla flavoring and extract are made with the extract of beans from the vanilla plant, a type of orchid that grows as a vine. The product containing coumarin is made from the extract of beans from the tonka tree, an entirely different plant that belongs to the pea family. Tonka bean extract contains coumarin, a compound related to warfarin, which is in some blood-thinning medications. Eating food containing coumarin may be especially risky for people taking blood-thinning drugs because the interaction of coumarin and blood thinners can increase the likelihood of bleeding."
Link -
http://www.fda.gov/forconsumers/consumerupdates/ucm048613.htm