It was the relationship with Faith and how it developed that really entrenched Angel as one of my all time favorite characters. I was a huge fan of his before "Five-by-Five" and "Sanctuary", but after that, he was just the man to me.
I really got the sense that Angel truly cares for Faith, and that's something she's never really had before. They only showed it the one time, but I always inferred that Angel visited her quite frequently in prison. It's very brief, but that was one of my favorite parts of the S2 opener.
I've always said that I don't think that Faith is a bad person, but that she's a very traumatized person who then had superpowers fall into her lap. I mean, you just knew bad things were going to happen in a situation like that. And I don't think she would have come back without Angel.
It's funny, but I've never thought of Angel and Faith being romantically linked. I'm not that far into the comics so I have no idea what happens there, but I've always thought of them as pure friends. A relationship with Angel would probably be really good for Faith though. I mean, he's about as good a guy as you're going to find.