Alcohol
Nicotine
Caffeine
Paracetamol
Cannabis
Cannabis is included because I tried it once, I am not a stoner.
I think drugs should be a personal responsibility though. Many drugs have their uses, as even the U.S. military is admitting with their amphetamine routines for pilots and such. But in any case, If people want to do stupid things that might get them killed, why should we deny them the chance to clean out the gene pool?