When Marcus thinks that Koromon had forgotten him after hatching, and Koromon reveals that he remembers everything. Marcus's reaction is priceless.
On the subject of remembering, when the DATS gang had their memories erased by Kurata after returning from the Digital world in the beginning of the second half of the season, it was pretty touching when Agumon got Masaru's memories back with their little punch-out.
When Ikuto felt rejected and Falcomon told him he loves him.
Ikuto once again in the bath scene with Masaru when he asked Masaru if it's okay for him to be with everyone in the human world and Masaru replied positively.