The 'gunni' is the name in New Zealand for a method of smoking marijuana involving a small amount of tobacco being placed in a thin metal tube placed in water in a (usually) plastic bottle (G-Force are preferred). In lay mans terms its a bong without a shottie and no cone piece. The tobacco is used in place of a gauze and for its headrush effect.
Light suction is applied to the bottle as a lighter is placed a reasonable distance away from the tube until all of the weed is burnt, as this occurs the gunni-er inhales powerfully on the bottle which sucks the burnt pot and the tobacco through the tube into the water, acting as a shottie effect and clearing the gunni.
These are also known as poppers
"Oi simo pass us the gunni mate"
"Right, lets go home and back some gunnis"
"Lets use your gunni, mines a bitch"
Gunni - Real gangsta niggas do not find anything "funny" because laughing makes them un-gangsta. So in order for a gangster to laugh without destroying his street rep, they say something is gunni (gangsta AND funny)
"I watched TV and this kid got shot to death
. It was gunni."