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