Enter "!!UNDONE!!" as a case-sensitive profile name.
Enter "PlumRugOfDoom" as a case-sensitive profile name. The terrorists at Prodigy will now have purple streaked hair.
Use the shield and have a teammate shoot it two times. If you now fall off a bridge, you may not take falling damage. This works about 70% of the time.
On any level turn, on "Friendly Fire". Have one player kneel down, then jump on top of their head. Next, have them aim at you with their gun. Make sure you have full armor. Begin jumping on their head. When you are at the highest point of you jump, have the other player shoot you. This is useful in Miami in the lobby, where you can use it to shoot people up in the hole in the ceiling.
At the B bomb (Counter Terrorist spawn), there is a way to get on the roof. You will need two people to do this. When you start, turn around and go to the bombed out "house". Jump on the bit of the house where you can, then jump up to the next part. If you need a running jump, you should use it but it is not necessary. You can now jump onto the tank. Run to the end and jump onto the boxes. Get one person to crouch down on the boxes and jump on his head. You can then jump onto the roof. When the Terrorists arrive to plant the bomb, you can take them out. To benefit the Terrorists, you can stop the Counter Terrorists from defusing the bombs.
Across the street from the bank at a theater, there is a billboard that reads "Half Life: The Movie starts Friday at 11".
Get three players on top of the S.W.A.T. truck. Go to the edge and pile up on top of each other. Then, have the top person try to jump onto the billboard. Note: This may require a fourth player.
At the Counter-Terrorist spawn point, take a right and go over to the fence. Throw a smoke grenade over the fence so that the people on the other side cannot see you. Run straight back to the wall so that the fence is a slightly away from you. You should be able to see through the smoke, and shoot.
The best map to use this trick on is Militia. Join a Militia map and play as a Counter-Terrorist. This will give you a closer position to the glitch. When you start, buy a Smoke Grenade. Then, go through the tunnel to the left which leads to the fence and the rocks that make a ladder over the fence. Jump the fence and turn to the left. You will see a rock hill. Go up the hill, but do not jump off. You will see a crack between the rock and the wall. Take out the Smoke Grenade, point straight down in the crack, and throw it. You will hear a crackling, like popcorn. Also in the terrorist spawn point on Miltia, there is a bed. Take a smoke grenade and get on the bed. Look down in the corner of the foot board. Throw the smoke grenade in that crack.