For Origins:
Morrigan- I adored her friendship arc so much more than her romance arc. The way she gets emotional and tingly after realizing her own social shortcomings and seeing she does have others who care for her really grew the character on me, far more than a romance arc ever did. Even if she disapproves of heroic type characters, I like that she is willing to disagree and occasionally make smart remarks but not totally up and leave everytime the Warden does something she doesn't like (or, Maker forbid, disagree with her). She's like that friend you love deep down in spite of all the crap because you know she's going to be there whether she likes it or not.
Sten- Love having him as a friend, even if his circular Qun conversations are a pain to get through. The first time I had him call one of my Wardens 'kadan' turned his character from irrelevant to likable.
Shayle- The whole dialogue with her was rich, and the more she liked you the funnier it got.
Wynne- A companion that asks how YOU are doing and looks out for YOU, even if some of her advice is unsolicited? Yes! Loved her since my first ever Origins run.
For DA2:
Aveline- By far one of the best friendship arcs. She basically lends her sword to help your family against the darkspawn and watches over you like an older sister. Even in a recent run where I had her on full rivalry, including the scene where she had no more words for Hawke, in the end she encouraged Carver to reconcile with me before the fight with Meredith, not to mention the last conversation before the final battle she still stuck around despite driving her mad. Gotta love that lady. She's a huge softie.
Isabela- The crazy friend you love, even when you hate her. Having her as a bff, dirty puns and all, really adds to the experience. In a party full of broody types, she lightens the mood and reminds everyone not to take everything so seriously. And when she has your back, she really has it. (Harkens back to post-Arishok tavern scene. She pushes Hawke away because she doesn't want anyone too close to her, yet their friendship prevails and she learns to trust others. Love it).
Varric- Even if he's not my favorite character (*dodges rocks from potentially blasphemous statement*), he's awesome as a friend. Another one willing to ask how YOU are doing and not asking you to fix his life. I felt his conversations allowed us to develop Hawke better and much more personally.