I'm most interested in Dorian, Iron Bull, and Vivienne, but I'll probably use everyone to some degree. People can surprise you.
My first run of Origins, I settled on Alistair, Leliana, and Wynne to take with me, and spent a lot of time with Morrigan as well. I didn't give the others a chance. On consecutive playthroughs, I really learned to love each character, much to my surprise. I didn't think I'd like Oghren or Sten, but both had really good stories. (At least, until Awakening. I felt like Oghren back-tracked a lot from his progress at the end of Origins.)
In II, I thought I'd love Anders or Merrill, because of Awakening and the Dalish Origin. However, they were my least favorites. I grew fond of Aveline, Carver when available, Isabela, and Sebastian.
In short, I'll let the characters speak for themselves, even if there are some I'm more interested in seeing right now. I could not want to spend any time at all with those three, and turn out loving some of the others so much more.