In the graphical update, the Glock pistol is changed to a Beretta. The Beretta cannot fire underwater, yet both can do so in the game.
In the graphical update, the MP-5 is replaced by an M-16 derivative firing 9mm ammunition. While it is possible that a security force may be armed with such a weapon, the military would use either assault rifles or MP-5s.
Valves are shown to turn in either direction to open or close, when the standard is to turn right to close and left to open.
An elevator that the Player is in starts falling. Elevators are specifically designed not to fall.
The best and helmet that the Player uses should hardly be effective protection against radiation and other hazards.
'Tony's Pizza' off the Black Mesa Transit System has no railing.
The Player is not issued any more rounds for his sidearm than are already in the magazine, which is unwise for security personnel.