Sorry to dig this up after so many days, but I didn't notice this until I logged in to Steam today: Robert Culp was the voice of Breen in Half-Life 2.
Direct from Steam:
quote:Robert Culp August 16, 1930 - March 24, 2010
We were deeply saddened to learn of the death of actor Robert Culp on March 24, 2010. We were fortunate enough to work with Culp during the making of Half-Life 2, when he wrestled invisible headcrabs, expressed a passionate interest in animation, and taught us all how to bring a character to life from words on a page, as he voiced one of gaming's most beloved villains, Dr. Wallace Breen. He will be missed.