Thing is, there are already so many millions of different drugs that do different things you'd be hard pushed to think of any affect (oh cunt, that should have been 'effect' but IR has already quoted it for posterity) that something somewhere doesn't already have to some degree. Apart from something obviously impossible like a drug that makes you invisible - although a drug that makes you
think you're invisible might be pretty amusing, at least to other people.
I'd go more with certain existing drugs with their annoying side-effects or after-effects removed, eg.
* a drug identical to ecstasy in every respect, but without the inhibition of physical sexual function - I think anyone who invents this would deserve every Nobel prize for chemistry from now on, for ever and ever
* or, something like acid or mushrooms that doesn't give you the distinct impression that you're losing your mind - though this is of course inseparable from all their other effects
* or, an opiate you can enjoy whenever you like without building up a tolerance, getting addicted or suffering constipation from hell,
* or, how about a hangover-free version of BOOZE???
yeah it's all about perceptual changes rather than the buzz.
Something like acid that only worked in audio would be wild.
Drug nerd that I am, I've read that diisopropyltryptamine (
DIPT) has very interesting audio effects - not that I've tried it, it's not really the kind of thing your friendly neighbourhood dealer usually carries. I imagine it'd be a bit like asking for clarky-cats or triple sod.
Edit: damn, shoulda known tryptych would get there first on this one, his name says it all really...