My favourite character would be Anders. For once cause he is a recurring character soo I felt already a bit attached to him and he is also a key figure in story while all your other companions have almost zero impact on anything (apart from maybe Isabella and the book but not really). I also have a thing for mages in general. ;)

The whole Justice/Vengeance thing was interesting but I feel like they could have explored that much more. 

He was also my love interest for the same reason as mentioned above cause given his role in the end act it adds a bit of drama to the romance (even though I obviously didn't know that in the beginning). Overall he was a bit emo and annoying with his constant whining though.

I also really liked Carver, I think the dynamic between him and Hawke is interesting and it's a shame he was hardly in the game. His character development is also enormous compared to the other characters (at least when made a Warden).

Was happy to see him back in Legacy and MotA.

Varric and Isabella provided a lot of funny dialouges and companion banter (Isabella and Farris/Aveline are priceless together) but otherwise remained to shallow. 

On the other hand I hated Merryl. She annoyed me to no end. She was the only companion I had locked on full rivalry cause I always used the aggressive dialouge option to cut her off short.