Get a bunch of inventive contractors together with a case of beer, and you get the beer cannon. Give the idea to a robotics major fresh out of college and you get a less destructive, but still useful version.
Recently, engineers from the Forest Products Laboratory (FPL) have been having almost as much fun (sans beer) with the debris launcher, an air cannon designed to launch 2x4s at test walls. Of course, engineers have been doing this for quite some time (see, for example, the Texas Tech wind cannon), but this time the goal is to come up with a more affordable tornado shelter. Most safe rooms are constructed from concrete (see FEMA's "Taking Shelter from the Storm"); the FPL has been charged with designing a safe room from wood.
According to an article in the Milwaukee Journal Sentinal, the research team has found that a wall made of three layers of staggered 2x8s seems to work best under fire from the debris launcher. Each 2x4 missile leaves a two-inch deep impression, but usually doesn't bend the interior wall. If the interior wall is bent or broken, that's considered a failure.