Hoodia is supposed to be the next big thing. Lots of 'hoodia' out there, it might not hoodia at all. It binds to a glucose receptor several logs more potently than glucose. I've got TD (with green tea) - it does work, but really I was after the EGCG from it.
Its a good question.
Legal side I'm a bit stumped. Coca tea would be but unless you are in South America I wouldn't bother even if it appears legal - just go hungry.
Cat's claw????
Oh of course ... go green tea. Check my thread on different green teas. There is a slight problem of the caffeine content, but it is supposed to be low (4-fold lower than black tea). this is debatable. Thats the answer the answer. IF you wanna give Hoodia a go, report back but at present it might not be effective.