Counter Strike Source.
You'll find tons of stoners there that would love to communicate while playing with you about being high or tripping out.
Hard to remember when I didn't join a random server that had names like:
High all da time
bongtoker
token4life
MARIJUANNA
LEGALIZE MARIJUANNA NOW
Raul Duke
Gonzo
ganjaninja
Bong
stoned right now

and yes, those are actual names i've encountered or at least similar.