Cass is my #1, because she's a kickass sweetheart and she's my favorite potential Batman successor. Then Damian because he's obnoxious and cute, and I like to see him learn and grow. Like watching your own kid.
My #3 changes depending on what I've been reading lately: Right now, it's Jean-Paul (pre-FP especially). Not only because he's sweet and kind, but seeing him fight as Azrael freakin' rips LOL