Use the mic in single player. If you keep the mic plugged in then you can issue voice commands to your team, saves you having to take your finger of the trigger! Whatever Keller says, you say into the mic, the team do it, as if you had pressed the button.
Entry Alpha spawn library. Have every team mate have Motion Sensors, and place them all on one of the white turnstiles, and it will have to be loads. When there is enough, you will be able to enter the library section, by walking into them all.
Note: It is hard to do this correctly, so keep trying.
Left & Right Walkway Glitches. You will notice the plant pots sticking out of the sides of the walkways, 3 on either side. If you hug the part next to the plantpot, and not on the plant pot itself, you will be able to shoot down, and see down the walk way, without them being able to see you.
If you hug the wall to the left on the window in the library near Bravo Spawn, you will be able to see down the Walkway, shooting the oncoming and invading Alpha Team!
The Glitch Window!
The most annoying glitch in the game, as it covers the back exit from Alpha spawn, right office, bottom left area, and the right walkway! Mostly used from members of Bravo Spawn. It is the room next to the Libarary, and if you hug the wall to the right of the window, you are Mr. Invincible! Unless someone comes into the room also, or you get bombed XD
When you play the Fremont Street level look for a ledge on one of the buildings that has a bottle of Axe cologne. When you shoot the bottle the neon roof of the Fremont Street Experience will change to an animation of a girl in a bikini promoting Axe items. This sequence is then followed by a sequence with outtakes and early animations.
Again you probably have to be in a ranked-match to do this.
1. On the level 'Wartown' (you must download the black-pack first, luckily it's free) spawn on the second floor of a building which has a turret on a box on the edge of a hole in the building-i don't remember which side that is, sorry. Once you spawn, go straight out of the room, past what looks like an ice-cream container, across a small plank forming a tiny bridge, throgh the next doorway next to a broken ladder, and you should be in a room with a flight of stairs and a turret in a window to your left. Be standing and stick on the wall on the left of the turret, make sure you are close enough to use the turret. Stay on the wall-while standing-and hold a while loking at the turret untill the turret dissapears and your gun is there instead. You'll know it worked if you get off the wall and the camera is in a third-person view and your arms are pointing at the turret. Now you can take the turret with you (the turret will not appear in your hands and you cannot get on cover, but you can still shoot people).
I don't know if these will work at any other time than in online-ranked matches.
1. On the level 'Killhouse', when you go up to the roof, crouch at the top of the stairs and walk down them sideways (hugging the wall) untill you can see through the very top of the wall-where it meets the floor of the roof-now you can see the other base's roof and shoot them while they can only see the very top of your head.
2. On the level 'LVU Campus', go to the roof and have a teammate crouch between the AC thing, to your left after you get to the roof, and the wall. While he's there, you take cover on the side of AC that is facing the wall which the doors are on, look up-as if you are about to shoot someone-and as soon as you do let go of the left trigger and you should be on top of the AC. Now walk over your partner onto the wall. You are now able to run around and snipe peole. (you can still die up there, though).