For me is Alfira. I could listen to her the whole day, and would love to travel with her and talk more. The second would be Astarion, his VA is just having so much fun with the character. And then Shadowheart, she is a great VA, she really knows how to make me want to slap her in one scene and cuddle her in another.
I personally think all the VAs are great so far, but these are my favorites.