I'd like a drug that makes me obsessed with the activity I'm doing during its consumption. The effect must be temporary and its duration controllable -- e.g. it may depend on the amount of drug consumed.
(The game designer in me wants to come up with a downside to balance out the benefit. I'm not sure what negative effects I'd like this drug to have, but I definitely don't want it to induce burnout afterwards.)
One possible downside is that it might prevent useful mental flexibility. Would you notice if the fire alarms went off?
We operate like this: the "overseer process" tells the brain, using blunt instruments like chemicals, that we need to find something to eat, somewhere to sleep or someone to mate with. Then the brain follows orders. Unfortunately the orders we receive from the "overseer" are often wrong, even though they were right in the ancestral environment. It seems the easiest way to improve humans isn't to augment their brains - it's to send them better orders, e.g. using drugs. Here's a list of fantasy brain-affecting drugs that I would find useful, even though they don't seem to do anything complicated except affecting "overseer" chemistry:
1) A drug against unrequited love, aka "infatuation" or 'limerence".
2) A drug that makes you become restless and want to exercise.
3) A drug that puts you in the state of random creativity that you normally experience just before falling asleep.
4) A drug that puts you in the optimal PUA "state".
5) A drug that boosts your feeling of curiosity. Must be great for doing math or science.
Anything else?