Half-Life 2: Accelerated Back Hopping - Page 1
This is actually a glitch I managed to do that someone else found out. It involves tricking the game into thinking you're moving forward, and when the game tries to apply force back to slow you down, it instead pushes you the direction you intend to go and the more you do it, the more force is applied. If done properly, it can make the player reach ballistic speeds and finish chapters much faster than normal. It completely replaces Bunnyhopping which was an old Quake method of movement that was recently patched.
A video of me successfully attempting this (but not actually going at "ballistic" speeds) can be found here: [font=verdana]http://www.youtube.com/watch?v=_EBeoNWcmJs[/font]
And how to pull it off can be found here: http://wiki.sourceruns.org/wiki/Accelerated_Back_Hopping
Example of a speedrun using it: http://youtu.be/NV-AWxqYAgc?t=41m46s