What is the single most impactful nootropic you have ever tried and why?

Dihexa, so far. I shared my experience here My Dihexa Experiment / Experience

Also Monatomic Gold, Rhodium and Irridium mixture that I used to buy from a store called Tibetan gold was great. It was making me sleepy right after taking it for the first few weeks, but it is great product. Makes me more consciouss overall, more pure and divine.