Pretty much the only drug that won't kill you is marijuana. Alcohol can kill, coke can kill, heroin can kill, etc...
I don't try and act cool because I smoke weed, its just something I do with friends for fun. It doesn't make me "badass" or "cool" like some people think it makes them. Some people are against them completely, but I could see marijuana legalization and sales bringing the US out of debt.
TL;DR: Do drugs, but stay away from the hard drugs like coke, heroin and meth.