Tongkat Ali is what was referred to above, and I can 100% swear by it.
Its a root that is harvested in Indonesia and basically increases your body's
natural production of testosterone. It works differently from things like steroids and pro hormones because its your own testosterone that is being produced and NOT something like steroids replacing your natural testosterone producing functions which makes your own production shut down. Thats why steroid users commonly have ball-shrinkage. Instead, the area in your testicles that produces your testosterone (look up 'leydig cells') is working in overdrive and not being replaced.
I've found a legit seller on ebay that sells the real stuff and not the small dosages that you can find in common supplements (and I'm in no way affiliated with them). You have to get a potent extract in order for it to work. Heres the link:
http://newlifealternatives.com/
I'm actually surprised I have seen it mentioned here as much as it was in Thundersplace. ?
Anyway, I taken it for the last two years and its pretty insane how much it works. After being on a cycle for only 4 days I could actually feel my balls being fuller and bigger, as well as being in a better mood with more energy. The only downside I could find, if any, was that if I tried to take an extreemly high dosage for awhile, I could get a little more aggressive than usual, but thats about it.
Check this site out for more info :
http://www.asiatour.com/tongkatalisize.htm
Hope this helps!