Resveratrol is on my "maybe" list. I'm seeing some really interesting research, but the good stuff may end up being patented and sold as a drug, which sucks.
I'm still a Vitamin C fan, even though it's fallen out of favor. Seems to help when I've stressed out my system through alcohol or other chemical irritants.
Also on my "to-watch" list is delta tocotrienols, one of the components of vitamin E. Saw some interesting evidence that it might be good at actually helping to remove coronary artery blockage, but it's still WAY preliminary. And no, that's not a recommendation for vitamin E itself, which in larger doses can cause all sorts of problems. Just the delta series.
The B series of vitamins are interesting, as there seems to be a good-sized gap between the amount most people have in their bloodstream and the amount that they can carry easily. A little dose of B-12 seems to help me enormously with concentration. At least for a short period. YMMV.
Note this is all subjective, and based on half-assed research and gossip. That's one of the rules in this arena: there are no rules. :)
What would the other 2 or 3 be? I've found Vitamin D (taken as a liquid) to be one.