D-aspartic Acid - new but effective - I can actually feel the effects
LJ-100 (not taken simultaneously with DAA) - I can also feel the effects.
Zinc - rather hard to say because it's conditional on a person being deficient (i believe many many ppl are not at optimal levels). It's effects on T can be dramatic if a person is deficient.
Many ppl report higher test levels (and had blood work done to prove it) from taking Alpha Male, TRIBEX, or rez-v (not simultaneous)
With tribulus the source and handling of the materials is crucial. Many products are garbage, so the studies you see out there are hard to sift through. I believe Biotest did their own studies on this, and also as I said, many ppl have reported higher test levels from having blood work done before and after taking Biotest products.