Favorites, huh? Hmmm. (Someone please correct if I got some of the names wrong.)
::
Female ::
Aya Hisakawa - for her elegant and mature roles
Kikuko Inoue - for her charming, big sister appeal
Fumiko Orikasa - for the clarity of her cute voice
::
Male ::
Ryuusei Nakao - for his roles in Hundred Stories and Gakkou no Kaidan!
Toshihiko Seki - for simply sounding cool and recognizable
I have other favorites, but they're mostly due to a specific character that was played. So, I guess that would mean I like the characters more than the actors/actresses themselves. (i.e., Quon in RahXephon, and Lum in Urusei Yatsura)