We don't use much slang but we have said some funny things. One thing was...

"Man, I'm all the way at wal*mart!!" ~ Meaning: Dude I am so high I am [this far away] from this place.
~Depending on how high we are we will substitute different locations.

The other word we came up with is also a rule.

"UNO!!"

Meaning: I get first hit. This rule can only be in use though we at least one person still already high from either previously in the day or from the bowl/joint/pipe/blunt from earlier in the day.