Jak II : Renegade

Go to the South city water area and into the left corner (there should be a small square building with a door). Jump on the roof, orient your camera facing back towards the center of the water area, then roll off just above the door. If you do it right, you will hit the ground, the door will open briefly, and you should be able to get inside. Once inside, you can use R3 to look around, or press up on the camera repeatedly and you will suddenly be in an elevator. At the bottom of the elevator is a cool platform with blue stretching in all directions. You can kinda see the block puzzle in the upper left corner. When you die there you will reappear next to the Titan suit in the underport. This glitch cannot be accessed until you get to "Rescue Sig in the Underport".

After the cutscene before the final battle, hold R2 and you'll transform (or stay as) Dark Jak, regardless of Dark Eco meter.

It is possible to destroy Errol in the final race. All you have to do is force him to hit a wall (the large rock one works best). He will not regenerate and the cutscene once you win the race remains the same. This does not work with other races and it is also possible for you to be destroyed as well.

If you are angry for whatever reason at the Krimzon Guard, and want to make them mad and not get killed for it, then complete these steps:
1- Get a Zoomer (they're the small fast little vehicles)
2- Go full speed aiming towards a guard
3- Right before you hit him, press Triangle to mount off
4- If you do it right, the vehicle will smash into him and he will receive damage, without raising any alarms

To instantly remove alert status, walk into an airlock for a City exit (do not leave the city). The music should immediately fade and once you walk back into the city the alerts will be gone.