love doing opiates by myself, whether its heroin, oxy, dilaudid, etc.
i've only actually IVed oxy and dilaudid though. i mostly used to do them by myself since i don't have any other friends who would really do them with me, and i don't really tell a bunch of people that i break out the rigs sometimes, which leaves me by myself. i prefer it anyway, since i can just watch a good movie, or not having to worry about scratching my nuts too much or something lol.
i didn't vote for marijuana, even tho i love doing it by myself, i still like smoking with other people occasionally too. with opiates tho, i'm like 99% of the time doing them by myself.
come to think of it, i do a lot of substances by myself. i even enjoy drinking alcohol by myself sometimes (not saying i prefer it to going out, but sometimes there's nothing like getting completely fucked up by yourself and getting to know yourself a little better).