Oh boy there's a few of them
Shayle was incredibly well crafted, hilarious dialogue, and definitely an awesome party member both gameplay and personality wise
Zevran was a heart-breaker as being so morally ambiguous that you could see the good in him yet you know deep down he could turn on you and leave in a moment's notice
Wynne was neat in the sense of her protective, motherly nature and the fact she didn't let the likes of age or typical female tropes slow her down
Fenris was my favorite DA2 character. He's got an incredibly polite side (you're allowed to disagree and he respects that, much unlike a certain whiny mage), he's got a soft side and is jealously by your side. Plus he's a warrior...an elven warrior...nice to know there's some diversity amidst the tropes
Varric was well written and so opposite of the typical dwarf (Scottish brogue, crazy warrior, overly proud)
Aveline was one of the most inspiring characters in terms of her dialogue (I still use that phrase 'you turn the page when you're ready' from your dialogue regarding her deceased father, so powerful in terms of wisdom and letting go when you're ready, not when others). She's got wit and the fact she didn't fall over Hawke and had her own personal preferences that didn't include him/her
Isabela was another well done character. She's free-spirited and easy-going, almost a female Zevran, but upon seeing the rivalry romance, I saw one of the most complex, powerful characters in Dragon Age. I'm not for returning characters but I'd love to see more of her around, possibly for DA3
Bethany/Carver were really well done siblings with complexity.
And some of my favorite NPCs:
Herren and Wade. Most hilarious couple in DA thus far. Love the bickering and whining between them. They sure do make some effective armor that's for sure!
Grand Cleric Elthina. Instead of everyone in the Chantry being portrayed as a religious zealot, she comes off as maternal and peaceful, someone who actually practices what she preaches versus becoming politically minded
Branka. She was a handful, loved the attitude and twisted mindset. Her overall relation to Oghren made her interesting and more memorable (and I love the accent)
Bryce and Eleanor Cousland. Tough, awesome parents who go down together. Nice knowing in-game parents have personality instead of being mere plot devices to exist solely for the sake of being biological parents
Leandra Hawke. I actually really liked her and still get choked up when I see her die in my DA2 playthroughs. You just want to save her not to meta-game but because she's really a good person despite being a noble (she's not snobby, mean, or downright rude, and she's willing to help people)