This is the video that started it all! I've since made 2 sequels to this video, called 'Till Death Do Us Part' and 'Till Death Do Us Part Two', the latter of which won 'Best Drama' in Valve's Saxxy Awards in 2013!
To clarify, the 100 hours working on this included the time for planning, map/location scouting, posing, lighting, camera keyframing, and all the actual rendering (in maximum DoF and Motion Blur settings, in 30fps). It easily stacks up.
Inspired by Ubisoft's trailer for 'ZombiU' that premiered at E3 this year (http://www.youtube.com/watch?v=8ZbsXF...), I decided to create a similarly cinematic animation with the Team Fortress 2 characters facing off against zombies.
Final animation was rendered out in 512x DoF and 128x motion blur, in 1280x720 and 30fps.