Below are a list of keypad codes in the game, sorted by applicable mission, so you don’t have to figure them out yourself.
Mission 1 - Police Station
Keypad #1 - 091772
Keypad #2 - 5929
Mission 4 - CIA HQ
Keypad #1 - 7687
Keypad #2 - 110598
Keypad #3 - 2019
Keypad #4 - 110700
Keypad #5 - 0614
Mission 5 - Kalinatek
Keypad #1 - 97531
Keypad #2 - 33575
Keypad #3 - 1250
Mission 8 - Chinese Embassy, Part II
Keypad #1 - 1436
Keypad #2 - 9753
Keypad #3 - 1456
Keypad #4 - 1834
Keypad #5 - 7921
Mission 9 - Presidential Palace
Keypad #1 - 2126
Keypad #2 - 70021
Keypad #3 - 66768
Hint: Sticky Cam Uses
Once you acquire the SC-20, you can fire sticky cameras. What you may not know is that you can fire them at the heads of enemies and knock them out without using your other weapons.
You can also pick up the sticky camera after you fire it (provided you can get to it) so you technically have an "infinite" number of chances to stun guards and other people.
If your camera is fire into a spot that you can't get to, you can try firing on it to "bounce" it somewhere where you can retrieve it.
Cheat: Unlock Everything
Enter !walk_thru! at the profile (create a new one).