Never been inclined to do drugs before/during sex.
I've heard 420 has some nice effects, but I don't smoke. At least, not that...
Alcohol would probably be the most common thing I've used, but not for enhancement.
It's usually just an ice-breaker for both of us to get comfortable and relaxed.
I find that, at least for me, impaired sex is less exciting and fulfilling. I'd rather have all my faculties at peak receptiveness, or at least close to it.
Although I do have this fantasy about fucking a drunk chick...
but only because when they're drunk they're more likely to say Yes to someone they probably wouldn't consider otherwise.