Me and my friend have some that we made up ourselves... it goes along the lines of this.

If we want to smoke a joint/blunt we say to each other (so noone knows what we are talking about)- "Hey, do you want to go talk to Titus?"
The reason being joints/blunts need to be tight as fuck, or titus fuck, so we say Titus for short.

If we want to smoke out of a pipe/bong we say to each other- "Hey, is there anyone in the bathroom?"
The reason for that is what is in a bathroom? A toilet-BOWL? Umm yeah, kinda like secret code for pot smokers if they don't want other people to know what they are doing.

Also, people say they want "greens" a lot and stuff, which deals with the first hit. But we just say, I want to be greenskeeper, or I've got greenskeeper... just another way to say it, plus we made it up and it feels good to use lingo you made yourself.