On the HellBender's back license plate, underneath the name of
the driver, it says "Licensed to Frag".
On rocket launcher ammunition, there is a label that says "WARNING:
If you touch this, then you have a problem."
There are play, pause, stop, and eject buttons on either side
of the Bio-Rifle.
On Minigun pickups, the smaller gear (that is visible in first-person
view) is missing.
In the Deck 17 level, there are labels on the large crates near
the ASMD pickup. The labels read: "Extreme Temperature Containment
System: Magma (Avg. Temp 1170°)".
In some levels, there is a blue screen with scrolling text on
it. The text reads as follows:
"There is no reality. There is only this. This time. This
place. This Contest. Be the best. Unleash your power. Lead your
team in a battle of the mind. Win the Tournament. If you can't,
step aside for someone who will.
Keep your eyes on the prize, and your finger on the trigger. If
you're reading this, you're already dead."
On the side of the link gun pickup, where the energy conduit connects
from the battery to the gun, there is a small label on the side
of the battery housing that says "Hose Goes Here You Stupid
Dumbass". Also, underneath where it says GBR-22 on the side
of the barrel, it says "Generative Beam Rifle", which
is obviously what GBR stands for.
On the side of the Redeemer missile, it says "Swallow This!"
There are also several secret rooms throughout the game, that
one can only access by enabling the ghost code. These rooms
do not have anything in them, and they are usually simply concrete
walls, floors, and ceilings. However, somewhere on any of the
walls, floor, or ceiling, there is some writing, that usually
says either "What are you doing here?" "You're
not supposed to be here", or "Cheater."