Well, Johnathan, the protagonist, is the obvious choice for "favorite" as it is around him that the action revolves.  Johnathan has a lot of growing up to do, even though he is brave and dedicated.  Only thirteen when he joins the Revolutionary War, and  "(d)uring the next twenty-four hours, Jonathan discovers a great deal about fighting, soldiers, his father, and himself. He must decide who the enemies really are and how he feels about them. 

By the time the twenty-four hours are up, Johnathan not longer sees the world in black and white, overcomes prejudices, and finds himself a much older thirteen year old than he had been just the previous day. 

For more information on Johnathan's adventures, visit the "Themes and Characters" page here at eNotes.  A link is provided below.