Please note that this is an incomplete list of designer drugs/research chemicals of which some may be illegal.
α-methylfentanyl, became well known as "China White" on the heroin market
3-methylfentanyl, extremely potent opioid, allegedly used as a chemical weapon by the Russian military in the Moscow theater hostage crisis
MPPP, especially infamous due to an impurity in some batches called MPTP, which caused permanent Parkinsonism with a single use
4,4-Diphenyl-6-(pyrrolidin-1-yl)-heptan-3-one, the pyrrolidine analogue of dipipanone and phenadoxone.
ALD-52, N-acetyllysergic acid diethylamide, famously believed to have been the active ingredient in the "Orange Sunshine" acid of the 1960s
ETH-LAD, which has been sold by some research chemical suppliers.
AL-LAD, which has been sold by some research chemical suppliers.
PRO-LAD, which has been sold by some research chemical suppliers.
5-MeO-DiPT, 5-methoxy-di-isopropyltryptamine (also known as "Foxy" or "Foxy Methoxy")
NBOMe-2C-C, 25C-NBOMe, "Pandora"
NBOMe-2C-I, 25I-NBOMe, "Solaris"
NBOMe-2C-D, 25D-NBOMe, "Divination"
Dizocilpine (MK-801; (+)-5-methyl-10,11- dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine)
Eticyclidine (PCE; CI-400; N-ethyl-1-phenylcyclohexylamine)
Rolicyclidine (PCPy; 1-(1-phenylcyclohexyl)pyrrolidine)
Tenocyclidine (TCP; 1-(1-(2-Thienyl)cyclohexyl)piperidine)
TFMPP, 3-trifluoromethylphenylpiperazine, has the unique distinction of being the only drug in the USA to be emergency scheduled into Schedule I and then allowed to become legal because the DEA was unable to justify permanent scheduling
PMA, a highly dangerous amphetamine derivative responsible for many accidental deaths
PMMA, similar to PMA
PMEA, also similar to PMA
Camfetamine (N-methyl homologue of Fencamfamine)
Flephedrone (4-FMC), and its 3-fluoro isomer 3-FMC
MDPV, Methylenedioxypyrovalerone, commonly known by its street name "bath salts"
1,4-Butanediol, another GHB analogue
2-Methyl-2-butanol, a more potent analogue of ethanol
GBL, gamma-butyrolactone, both a precursor to and substitute for GHB
GHV, gamma-hydroxyvaleric acid (4-methyl-GHB)
Methylmethaqualone, an analogue of the sedative methaqualone
Phenazepam, a benzodiazepine that was not listed by the Convention on Psychotropic Substances and so is not regulated internationally
CP 47,497 and its (C8) homologue cannabicyclohexanol
Madol (sometimes referred to as "DMT")
THG, "The Clear"