Tried most supplements (probably around 200), but regularly take B Vits and Zinc, Eye Q Fish oils.
And for anyone that states a balanced, healthy diet provides all you need - that's all very well, but some people still need more (depending on how your digestive system works, and how your food, diet is metabolised)
When I say that, I mean - one person can can 15mg of Zinc in his diet - and still absorb none of it (simply by eating the Zinc rich food item at the wrong time, with the wrong type of dinner) - whereas another person can eat the same amount, and absorb it all (simply by chewing it properly and having the necessary enzymes in his stomach to digest it) - And the same is true with fat / water based vitamins and minerals. Some people retain them well, others just pee them out and need constant supplementation.
So saying a healthy, balanced diet is all you need is a bit of a fallacy. Everyone is different. Try each vitamin and mineral (but resech beforehand on the way to take them as this is very important) and see which has a marked effect on you. Just don't overdo it, as too much of any of them is very bad.
On a side note, If you are interested in Nootropics

try researching DMAE - It really is astounding & a bit more than a multivitamin - but it's effects are simply amazing, although not sure if it's properly approved in the UK - but it sure as hell works with regard to Focus and clarity of thinking & it just proves that supplements really do work.