One product I used last year is Rev XP by NxCare. It helped me drop 25 lbs. in three months. It works great, without the heart-jumping-out-of-the-chest feeling I got when I used Hydroycut back in 2002 (when it had ma huang).
Once I've gained the mass I want, I may use it again. But, I'm eager to see what some of the newer fat-burners can do. So, I may try either Methyl-RIPPED by NxCare or Hydroxycut Hardcore.
I've considered using ThermoShred. But, I tried a sample of it a while back. It not only had me sweating, but my scalp was itching something awful. It felt as if someone were smacking me in the head with a cactus.