For me...depends on the group of people and the type of drug...
Chillin with some stoners, come cards, and some OE...def The Doors or Bob Marley.
Just smokin...don't so much need music if in a group, we end up talking over it...but solo...always, Pink Floyd or Bob Marley.
Droppin rolls...def trance/house but it has to be bumpin...and not outta some pussy ass ipod dock...so we either end up at the club or at someones house who can accomodate.
Just getting drunk and wanna party or dance...Reggae all the damn way!!