Trent, Kove, and The President of the Navy, definitely.
Much like the other procedurals, Trent definitely carries the show on his shoulders through a good chunk of the episode.
The President of the Navy is definitely the craziest character. An instant go-to guy for laughs. I love him.
And Kove is the breakout character. I did not expect her to be that great, but her serious tone and expressions, matched with insane dialogue, will never get old. Kate Mulgrew is fantastic as Kove, and I'm so glad she was chosen for this role for the actual show.
All three are great. I especially hope we see more President of the Navy in Season 2 (Although, I don't know if he'd make a good main character, yet)