1st Place: Automatic Zombie Killer 1.0 by Jesse Langston and Josh Olson
See a video of this in action: http://youtu.be/8SXHTdhITSw
2nd Place: Humanity Preservation Vehicle by Greg Myer and Sanjay Derbyshire
3rd Place: Knock Lock by Annemarie Kibbe, Corey McGee, Keith Evenson, and Tom Walker