Wolf-Shadow77 has been doing these little Half-Life cartoons for a few years now, but only recently have they really hit their stride, showing Gordon Freeman's universe in a way we're not exactly accustomed to seeing it.
The short animations use actual in-game sound clips, but then throw up visuals that upon first viewing, don't exactly match. By the time you're done, though, you couldn't imagine Half-Life looking any other way.
Wolf-Shadow77 [DeviantART]
[Axel787 @ YouTube, thanks Morris!]