Weird: Salvia - by far. If it actually works for you, it's a trip like nothing else. I can't really say it was good or bad... interesting experience the 4 or so times it worked, but no interest in ever doing it again. LSA was pretty weird as well, someone I knew (really, not trying to be cute) stole hundreds of Morning Glory packets from Home Depot and we split all of them on peanut butter sandwiches, it didn't taste bad! Also by far the worst/weirdest hangover... although it was probably more from the non-completely washed off pesticides than the LSA itself.
Rare: Peyote - Never even seen it available in the wild, but I did make it myself from cacti ordered online multiple times. It was MANY years ago, can't do that anymore, AFAIK. Best hallucinogen I've ever done, and I hate hallucinogens. Out of stuff I've bought? I've only gotten real opium a few times (all in Upstate NY over 10 years ago). Had a connec for Opana, but - (gasp!) - I didn't like it. Nowadays (at least in the USA) the rarest is probably REAL OxyContin, and getting rarer by the day!!
Dumb: This is just me, I know virtually no one else on the planet would agree with this - but pretty much every single hallucinogen. Mushrooms, LSD, etc. Even the ones I liked that I mentioned above, they were still pretty stupid to me. Big letdown. Barbiturates generally have zero effect on me, so they're dumb IMO as well! Benzos would go here too, but they at least help me sleep sometimes.