Doyle was probably my favourite of the characters but I have to agree with development side of Wesley, it was great to see the nancy boy become hard edged and decisive.
Cordelia is my favorite character in the Buffyverse, but I voted for Doyle on Angel, specifically. Such terrific promise, and a spectacular ending. What a shame about Glenn Quinn.
Wesley. Overall, I really liked the core of Wesley, Cordy, and Angel.
Gunn never made it past "recurring guest" status in my mind, and Fred only marginally more -- but Illyria was great. Linsay and Lilah were both great villains, but don't qualify as "favorites". I could have done with much, much less of Lorne.
I would have loved to see Kate become regular, though. Nina could have been fun to have around, too, if the show had continued, too.