1) Buffy: Buffy is my favorite character from any show or movie ever. I've never connected with a character more, she's a total role model and, speaking bluntly, I'm totally in love with her 🙂.
2) Angel: If Buffy is my number one, Angel isn't far behind. I find my favorite characters are the ones I can most connect with, and for whatever reason I do with Angel big time. I find self-sacrificing heroes really cool, and they don't get much more self-sacrificing than Angel. To me he's just the epitamy of cool.
3) Spike: I'm a huge Spike fan. He's one of, if not the, funniest and wittiest characters on either show and I find him a really deep and interesting character. He interacts so well with so many other characters. Buffy, Angel, Xander, Andrew, Giles, Dawn. They all became better characters after Spike was introduced. He's awesome.
4) Cordelia: I had a hard time not making her my number three. I love her on Angel. She's just the ultimate supporting character and I found I really cared about her. "You're Welcome" is one of the all time greats.
5) Fred: She's probably the single most likable character on either series. I mean, it's just about impossible not to like Fred. She's so nice and so sweet. And I love her relationships with the other Team Angel characters.
6) Wesley: I don't think anyone changes or develops more than Wes. I liked him and found him funny on Buffy, but when he moves to L.A. and joins up with Angel he becomes an awesome character. He's so tragic, and his final arc is just amazing.
7) Doyle: He wasn't around that much but I liked him in every episode he was in, which isn't something I can say about many characters. His humor and friendship with Angel was one of the best parts about S1 and "Hero" is just spectacular.
8) Xander: I'm mainly talking about S1-3 Xander here. Before he left high school, he was the funniest character on the show. He annoyed me at times, but the vast majority of the episodes I found him hilarious. And there was something about him always punching above his weight class but still being loyal that I really liked.
9) Giles: Basically, everything pre-S6 with Giles I liked. I loved him as the librarian/watcher in the high school seasons, but like a few of the characters I sort of felt like than just ran out of things to do with him. When he shined though, he really shined bright.
10) Lindsey: I loved Lindsey. He was a total flopper, but there always seemed to be more beneath the surface with him. He was a great bad guy and a great anti-hero. His return in S5 was so cool (and one I didn't see coming). Awesome character.
Honorable mention goes to Lorne.