I don't know how I missed this, but Dr. Don S. Davis, most famous recently for playing Lieutenant General George Hammond in the Stargate franchise, died on June 29. Apparently when he left Stargate SG-1 in 2003, it was for medical reasons, and he was only able to do a handful of appearances on the two shows over the next five the years, culminating in his appearance in Stargate: Continuum, which comes out on DVD in a week, exactly a month after his death.
The Stargate producers have spoken fondly of Davis over the years as one of the most professional actors they'd ever worked with (always knowing his lines before his arrival on set and always delivering them perfectly), and I get the sense that his lovable character General Hammond was really just Davis himself. The part had originally been written for him to be in tension with the SG-1 team, but Davis worked himself into the role, and they had to provide other characters to play that role.
I knew of some of his other work, especially as Dana Scully's father in The X-Files, but I didn't know that he had a Ph.D. in theater and that he had taught college-level theater for years. That doesn't surprise me at all, though.
For more, see the announcements of his death at Gateworld and SciFiWire and his entries at IMDB and Wikipedia.