Game-Breaker: The Art of Mijin. The explosion, while costing you a life, also restores your health meter, takes out nearby enemies, and deals a crapton of damage to bosses. More importantly, it respawns you in place instead of at the last checkpoint, preventing you from losing a large amount of progress. It also gives you another use of your special moves, so you could just use it over and over. (Until your lives run out, at least.)
I Am Not Shazam: Shinobi is a synonym for a "ninja" (specifically of its first kanji) and not the name of a particular character.
