From episode 1 of Buffy, he was my favorite character. I was so sad when he became just a recurring character in seasons 6 and 7. I've always just thought he was really funny, and his occasional badassness is always enjoyable.
I just adore Cordy, which is weird, because I didn't really like her in season 1 of Buffy. I hated the storyline where Jasmine was controlling her or whatever, because it so clearly wasn't Cordy. Ugh. So annoying. And then she just basically fell off of the planet.
Okay, obviously I had to include Spike. I think most people would rank him higher. I really do like him, though. Everyone thinks he's OMG SO ATTRACTIVE, but I just don't, which I guess is why he isn't higher on the list? Haha, I would totally be his best friend though. I think his character is great for comic relief and all, but I thought him and Buffy were horrible together. Just sayin'.
I've seen a lot of hate for him online, and I just don't understand how anyone can not love adorable little Andrew. I thought his character was so funny, and I loved his friendships with Anya and Spike.
I hated his character on Buffy, although the make-out scene with Cordelia was hilariously brilliant. When he came on Angel, his character somehow immediately got 10x better/funnier, while still being the same character. I guess it was better not having him always be playing off of Giles.
I thought she was a great minor character on Buffy, and I loved when she hopped over to Angel. She's such a pathetic vampire. I loved her as Angel's secretary, and I loved the episode where she thought she killed the guy she was on a date with. I was so happy when she got into the credits!
I was just generally really annoyed by Wolfram & Hart and everyone involved with it at the beginning, but Lilah grew on me for some reason. I'm not sure why. And I shipped Wesley/Lilah. Though I ship Wesley/Fred more.
My favorite potential. She's mostly an honorable mention because none of the potentials (except I guess Kennedy, but even her) really got that much screen time. There were just so many of them and they as a group were depicted as being more important than they as individuals, so we didn't get to see a lot of Rona. But she stole my heart in her first couple of scenes, and stayed my favorite potential until the end.