Some of the most proven nootropic compounds out there are things like Huperzine A, choline sources like CDP Choline and Alpha-GPC, and caffeine analogues like TeaCrine.
Huperzine A works as a reversible Acetylcholinesterase inhibitor. Acetylcholine is a neurotransmitter responsible for things like learning and memory. Because Huperzine A is an acetylcholinesterase inhibitor (inhibits the enzyme that degrades acetylcholine), it would work synergistically with a choline source like CDP Choline or Alpha GPC. This way you can optimize brain acetylcholine levels; you have a choline source like Alpha GPC (A-GPC breaks down into free choline and reacts with acetyl-coA via an enzymatic reaction to produce acetylcholine), whilst inhibiting the enzyme that breaks the neurotransmitter down.
On the other hand we have TeaCrine, which is caffeine analogue whose effects are very similar, yet last longer with no tolerance buildups. It's essentially a caffeine molecule with an added methyl group and ketone group. It sounds like a small difference, but these additions change the pharmacokinetics of the compound and its modes of action. The theacrine compound works on adenosinergic and dopaminergic levels much like caffeine does, while also showing anti-inflammatory effects and significant increases in wakefulness. Probably the most interesting thing about this compound is it's ability to deliver time and time again, due in part to its lack of tolerance buildup seen in test subjects.
All of these compounds are featured in clinically dosed, non-proprietary blends in ATP Nutrition's comprehensive pre-workout, Perform Kinetics