My drug of choice is oxycodone - but I can't get a hold of any which totally sucks , I'd kill to get my hands on some!
But basically I like it because you can enjoy it at a variety of different doses - low doses for going out and socialising, higher doses for just blissing out for an evening. There is no comedown or hangover, it helps you get some distance and think about problems you might have without getting anxious or irrational about them, and it's also great for dealing with hangovers and comedowns from other drugs making the day after almost as fun as the night before. Plus it feels great.
Shame I don't have the contacts to get a hold of it any more. Nowadays I mostly drink, smoke weed, and take the occasional tab of acid when I can be bothered with that level of insanity.