Alcohol, absolutely, beyond all reasonable doubt, is a drug that poisons people, and the illusion is that by drinking small amounts of it you are "OK."

Nicotine is an interesting one - you don't realize it really is a sort of drug until you do something like inhale while smoking a cigar or chew tobacco.

Caffeine... Man, I don't know. Chocolate has caffeine in it... and I just can't think of chocolate as this unnatural, poisonous thing to eat. I also think that while caffeine dependence may be a real and undesirable thing, we are not really at a point where we can consider caffeine as functioning as a drug, and thus I do not think of it as a poison.