I'm a fan of traditional, high-end nigiri served omakase style. My review is geared towards like-minded diners.
Having dined at Yasu and Zen in the past week, I can say with confidence that this place is the best place for traditional nigiri - based purely on taste - in Toronto. Every piece in their omakase (called "kyukyoku") comes with a lingering and sublime umami (which is why we're eating this, right?)
Lobster miso soup is also excellent, have it.
Update: they provided me a yubifuki (finger cloth to wipe your fingers with after each piece - you _are_ eating with your hands, right?) after I requested one in my reservation notes. Love it.