Groobo from speeddemosarchive.com posted this single-segment speed run of Valve's Portal for Windows PC. This is a dang impressive use of the tricks learned so far, especially since this was done in one sitting. The end credits are not included in the video. Timing starts from when the player first gains control of the character until the last piece of GladOS is destroyed.
There are at least two things that need to be explained about the tricks used. The first is that you move faster when you jump than if you simply walk. There's a bug with velocity though that if you jump, turn around in mid-air, and continue hitting the jump button your velocity will continually increase. This is why you see the player jumping backwards at a high rate of speed in some sections.
Another trick that's fairly new is the GladOS bug. GladOS is the boss of the game. Usually you have to use rockets and portals to slowly destroy her by knocking off pieces of her one at a time. However, a turrets bullets will still knock the pieces off of her, and there's no pause in between shots. This is how he quickly destroys GladOS.