20 - Khat
19 - Poppers
18 - Ecstasy
17 - GHB
16 - Anabolic Steroids
15 - Methylphenitdate (ADHD treatment)
14 - LSD
13 - 4MTA (manmade alternative to E, sort of like mephedrone)
12 - Solvents
11 - Cannabis
10 - Buprenorphine (Class C opiate)
9 - Tobacco
8 - Speed
7 - Benzodiazepene (Valium etc)
6 - Ketamine
5 - Alcohol
4 - Street Methadone
3 - Barbiturates
2 - Crack/Cocaine
1 - Heroin
The list compiled is from a UK study that analysed the relative effects of drugs; 1 being the most harmful and 20 being the list.
The whole drug classification system is messed up, particularly in the UK.
I tried coke once and I regret it quite a lot... stupid thing to do. Ecstacy is commonly thought of as really harmful, but it's only 18 on the list. I found that very surprising, and cannabis is higher than I though it would be.
If anyone's interested the scientists took into account the harm to the individual taking the drug, the harm to society and the addictiveness of the drug.