Back on topic, I have to disagree with everyone who thinks that the HL2 bullets are hitscan. Unless they've changed it since they made the traptown video. If you look in traptown, you can clearly see these white streaks of light (which is supposed to represent a bullet, I suppose) zooming past. You can even pause the video to catch one midair.
Moreover, there is a delay, be it two or three frames, between the muzzle flash from the weapon and the spark when the bullet hits the wall. It happens in more then one place in that video.
In addition, Gabe says somewhere in the Valve info thread that bullets are modelled sound sources moving at high speed through the air (i.e. you can hear a bullet moving past your head) and the emphasis in that sentence is the word moving.
Perhaps if Valve decided to nix that system and go back to hitscan, then the existing traptown video is at least a good example of the face that HL2 can support moving bullets.
Vino, gabe from valve told us that hl2 uses hitscan for most weapons. Those streaks of light arnt uncomon for hitscan in my experience. Personaly I dont know quite exactly why but meh. Its hitscan.