What are some of your past favorite Tennant episodes or moments? 
10 and 11 are pretty much tied for my favorite iterations, both special in their own ways. One of my favorite things about 10 was his care for "little" things while dealing with universe threatening events. From little shops in hospitals, to old men trapped in a box. The other generations cared about those things in their way too, sure, but he cared about them just as much as the biggest of things he had or would face. And not in a quippy way, where it could be played off as a gag, but genuine care. His run was just great.
*Another characteristic of 10 that I love - his core need/desire to give every foe he faces a chance, at times pleading with them to stop or change, not because he couldn't stop them, but because he genuinely would rather be friends with them, and would spare them the misery of dealing with what he ends up doing to stop them otherwise.