None of them.
If you read the fine print, they all say "These claims have not been evaluated by the FDA." They also say that the pills/whatever work best when combined with a sensible diet and exercise program. Duh, a sensible diet and exercise program works even without pills.
A lot of people are on here pushing diet pills that they sell. Anything that's sold on testimonials and not hard scientific data is suspect. And their supposed science data is never published in any real medical journals or publications or reviewed by any doctors not on the companies payroll.

ive heard slim quick (for women only) alot of ppl liked it

trimspa! Seriously it can work wonders.

I have used Silver Slimming Tablets by Silver Slimming Products Ltd and they worked very well. They are totally herbal. You are supposed to take 2 at about 10am and 2 at 3pm, but no later as you won't sleep, but personally I would start off with 1 in the morning and 1 in the afternoon for a couple of weeks to get you into it, or see how you go, as they can make you a bit shaky at first, probably because they speed up your metabolism.

To be honest the best thing to do is avoid, taking weight loss pills, and just resort to good old fashioned exercise.
As long as your burning more calories in a day compared to what your eating you should have no problems losing weight.
If you exercise 3 times a week for around a 30minute period then again you'll see improvements. Furthermore if the exercise your doing is interval based.
i.e work hard for 30s then rest for 30s and repeat say 10 times (which is only 5mins hard work) then this will have a greater effect for weight loss as fat cells are metabolised quicker through high intensity work.
Hope this helps i have loads more ideas with regards to training so feel free to ask away. thats what 7 years of uni studying sports science does for you.