The SRKFA cheat code.
Despite some BFG-esque paraphrases floating around, KFA actually stands for "Keys and Full Ammo". The SR is a Saints Row
-themed replacement for "ID", from id Software.
The NOCLIP cheat code.
Although made by the same company, linking "noclip" to the ability to walk through walls wasn't the case in Doom
(the relevant code there being "idspispopd").