2C-B.
I've learned so much and am so creative while on it. It brings me to a state where I am tripping and creative but still functional enough to actually play bass. I learned how to flamenco strum and play a lot of Les Claypool (he got me on the bass, it is his responsibility) songs that I would have never picked up.
Although amphetamines are great too. I once made an entire song using two synthesizers in one night, with almost no prior knowledge of songwriting or synthesizers. I just sat in front of the manuals, read both of them cover to cover, and let it all flow out. The song is incredible, but since I have no real interest in being a musician I gave it to my GF. She is an incredible musician, all I ask for is credit on the track should she ever get her off her ass and put a record out there.
Although to be honest, with how consistently good she is, I don't think she has ever done anything as great as that one song of mine in electronics. She almost admits as much (and it is hard for her, if you ever saw this bitch on the piano she would blow you away), but it is obviously very hard for a career musician to admit to being topped by a guy who just does it as a hobby.
It was a one hit wonder, however. It took me three days to compose and I fell into such a trance that I'm not even sure how I really did it, I mean I created all my own sounds from scratch, matched the drums with the bass with the melody and made it change at all of the perfect moments, and I have to hear the song again to go "holy fucking shit, how the fuck did I do this?" I'm not a musician, but I do have my one hit wonder thanks to amphetamine. It was like the music was moving through me and being created by some higher being, not like I made the song myself.