The climax of Inside the Illusion. It triples as a crowning moment for Senna, Sobek and, surprisingly enough, Keith.
Jalilblackmailing a religion in Brave the Betrayal. By knocking Senna out and threatening to destroy the African gods' afterlife by making her bleed on the tree that holds their Heaven and Earth together? And successfully pulling it off, with help from only two (David and Thorolf) conscious people? Jalil is fun like that.
David's personal crowning moment comes when he, while in a hopeless situation and less than a day away from dying, convinces Nidhoggr to help him, flies the gigantic beast over to Fairyland, helps him avoid the death trap set up for him, and simultaneously saves everyone's lives while resolving all of their problems. The same incident marks the first time in the books that he did something despite Senna's disapproval.