Lord Praven. He only shows up really in that one mission and a letter you get from him if you manage to talk him into going to Tython, but I think he'd make an excellent second apprentice once
I'd much rather have him on my ship than Lord Scourge.
Pretty much this. Praven's such an interesting character, I wanna know more about him (plus, I think he may also be an interesting romance option. Then again, this game already has an abundance of master-apprentice romances). I was glad to see him make another appearance on Corellia, but I just wished Bioware had paid a little more attention to his character model and stuck him in a non-Sith outfit and given him a Lightsaber color other than red, to show that he has really embraced the Jedi way.