Standard disclaimer: do this only between two people who've agreed they want to do drugs and have sex on them before taking any drugs
MD: fun, you probably won't be able to cum though, very intimate feeling with someone you care about, can obviously lower inhibitions and make you both be up for some things you wouldn't typically be up for, but again, you probably can't cum and that can be frustrating, especially if you're having a great time otherwise
Much more fun in my opinion is if your girl is on the subby side have her take the MD whilst you stay off it, you'll still be able to finish and she'll be super keen to make you happy and way more able to get into herself too
LSD: never had sex on it but I have taken LSD with girls who I would have fucked normally (either girls who I would have tried it on with or gf or someone else who I regularly had sex with) and I've got to say that was the last thing on my mind, never used LSD to party at all and fucking on it would be like fucking a library or fucking an academic topic, I don't know how better to put it than that without putting in more effort to think on it
Amphetamine (not methamphetamine, never tried that): never could even get it up so that's an instant no for me, never able to even jerk off as a result despite many people's tales of day long porn binges
Can't remember what other drugs there even are, didn't like sex on weed but I don't like weed anyway, I guess that's another thing to mention (because people above seem to like weed sex) is your mileage may vary, often these affect people differently