bk-MDMA- when you're hoping for the real MDxx it's a major, fiendish letdown, but I still enjoy Methylone in it's own sense.
Methylphenidate- like a more clinical version of cocaine (especially intranasally) with a ROUGH comedown.
Buprenorphine- such a half-assed, weird opioid with IME weak analgesic properties and an array of strange side-effects; it's annoying serotogenic stimmy, jittery peak effect.
Phenibut- IME it was such dirty, dehydrating substance that made my joints and kidneys ache the next day, all for a dizzying, weird buzz,
aPVP- Felt like this RC was designed to make humans go insane and the euphoria is strange
Lorazepam- The most depression-inducing BZD for myself
L-methamfetamine (Benzedrex)- literally awful jittery dysphoric stimulation with dopesick chills
Tramadol- dirty atypical opioid SNRI thing that causes seizures for me, and just in general is known for seizure activity