Synthahol! Could possible reduce so much violent crime it would be worthy of a nobel peace award!
A harmless drug that gets you to the point where you can enjoy yourself, but not so far that you became ill or lost normal control/reasoning. With an antidote pill that could be taken immediately after the social event so you could drive home.
ooh, it appears a controversial figure from the UK is actually working on this right now and has some very good ideas, even if this new 'drug' is by default illegal. If it works, then the governments of the world might be so interested they will write it up as a legal drug!