Well this shouldn't be around for long as it is going to completely frack up the Survival Scoring in Left 4 Dead 2. But like it or not the Skywalker Glitch is here in Left 4 Dead 2. Done by continuously switching weapons after being shocked by a pipebomb explosion lets players levitate for as long as they continue to switch weapons, allowing you to explore places through flight. But this video does a good explanation of how you do it, and the possiblilities are endless as you can do this glitch from anywhere after an explosion.