I was most familiar with him as Major Briggs on Twin Peaks and as Scully's father in a pair of episodes of The X-Files and he was excellent on both of those shows.
EDIT: Looking at IMDB, if you ever watched a TV show that was shot in Vancouver, you've seen his work.
He was a versatile character actor who seemed to always do a good job. I enjoyed him on SG1 and many other projects.
Looking at his IMDB page it looks like he did really get any paying jobs until he was in his forties and seemed to work a lot after that until his death.
I don't know quite how to put this into words, as I am actually very upset here about this news.
I'm a major fan of Twin Peaks, it's my number one show of all time and Major Briggs was one of my favourite characters from that show.
I think that this is a nice scene from Twin Peaks to watch at this time and perhaps to remember him by, if a mod could embed the video in my post or if someone could PM with details with how to do so then I will be much obliged:
As a Twin Peaks fanatic I've always wanted David Lynch to revisit the show perhaps with a new mini series of some kind, giving the show a finality - without Don S. Davis I no longer want this to happen, the show just would not be the same without his presence.
He was a great actor who played many of my favourite characters including Major Briggs and Scully's father in the X-Files, he was also a very nice man and was even scheduled to join the annual Twin Peaks Fest later this year.
I never watched "Twin Peaks", but it was a very nice to tribute to Mr. Davis. Dale, I sent you a PM on how to "embed" the YouTube video to your post.
For me, it will be very hard to watch "Beyond the Sea" - one of my personal favorite episodes of "The X-Files" again. What an incredible performance he gave in that role.
I love Stargate SG1 and Atlantis, so for me this is really awful news. Alot of us watch tv shows every week and in doing so it's easy to get attached to the people in them. You kinda invite these people into your house every week in a sense like you would friends or family. Over the course of a few years you get to know the characters they play and if you really are a fan you find out about the actors themselves. Some of us have even met them at cons and such. I've yet to have that previledge. Even though, I've grown attached to the stories and the incredible actors on the Stargate series that have brought them to life. Rest in Peace Mr.Davis.
We're watching Stargate SG1 on DVD (up to season 4, and I'm surprised to realize I"ve seen them all so far ) It's sad to hear of the loss of an actor that brought such a good character for so many years.