Ladies:
-- Hanazawa Kana (beautiful, soft voice)
-- Itou Shizuka (nothing needs to be said)
-- Paku Romi (i don't even know what her voice is for girl characters)
Dudes:
-- Nakamura Yuuichi (good emotion in voice)
-- Fukuyama Jun (i don't know...it's just memorable)
-- Nakao Ryusei (this guy's performance as Frieza...amazing.)
Kugimiya because... Well, it's Kugimiya, the Queen of Tsundere. She also has a really good singing voice. I really like her voice acting/singing in "The iDOLM@STER" games.
Asami because she does a wonderful job of doing both voicing both of my favorite characters of all time, Chihaya Kisaragi from "The iDOLM@STER" and Tsubaki Yayoi from "BlazBlue : Continuum Shift". I also think that she has the most beautiful singing voice in the entire freakin' world.