I know your joking,but best in what regards
I don't condone use of illegal street drugs but,Apart from it's soul destroying,life wrecking addictive quality,when smoked Heroin has very few bad side affects,less than Cannabis and other Class C drugs.
With that being said,it's addictive quality is what makes it one of the more horrible drugs.Maybe apart from Crack,I have never seen a drug which can completely take over a persons life.Given enough time,this drug will physically change how you look and even change your voice.User's need to use it on a more frequent basis every day just to feel normal,if they have a break they rapidly suffer painful withdrawals .
So yeah,it's maybe the "best" drug if your hell bent on messing your life up :
: Though if anyone has had extremely strong pain killers,Like Morphine,it is supposed to be similar in regards to how it feels.