Right. This is one I can only eat in public.
I like to take the "crab salad" gunkanmaki (that's the hand-formed ones with the "vessel" made of a strip of nori, wrapped around a small oval of rice, then the soft stuff spooned on top, the word means 'war-ship roll') and add about a half teaspoon of the freshest available wasabi.
Then eat it in one bite. This will definitely explode the back of one's head off. For some reason it also gives an intense flavor of umami (glutamic acid, an amino acid that there are specific taste buds for, the "fifth flavor" ... and I didn't know before I just looked it up, but Brillat-Savarin, the French epicurian who created the study of physiology of taste, in the "western world" anyway, identified a quality which closely matches this flavor, called "osmazome".)
Anyway. I will often start off and finish off a visit to a sushi bar with a mouthful of this brain-exploding wonderfulness.