Just press ~ (tilde) key, then enter one of this codes: 
 
kariya - max out Ammo 
corbet - Be Invisible 
drury - Get fukk ammo 
roy - Invincibility 
domi - Artilery strike
 
This is a small exploit which makes 
your missions MUCH easier.
 
First, save your game, then end your 
mission. Return to the mission screen,
and click Change Gear. You MUST change
at least one item of gear for this to 
work. Accept your gear, click once on 
your save game, and hit Start Mission.
You will be returned to your saved game
with the new gear you chose, a fresh 
(full) load of ammunition, and full 
health.
 
This exploit is terrific for missions 
that combine long-range combat with
tunnels or buildings.
 
Reload:
 
If you save your Mission, when you reload
the Mission, your Ammo is back up to Full.
 
Remember that you lose your scope view 
whenever you reload your weapon.
 
Press `~` (tilde) and enter the command you want.
  
Command Meaning
  
PuntCRC Punt CRC
PuntLog Punt Log
scopescale Scope Scale
Punt Punt
Bozo Bozo
Verbose Verbose
savescores Save Scores
dualcpu Dual CPU
Gimme Gimme
exit Exit Mission
quit Exit Game
sky Sky
flipmouse Flip Mouse
hudcolor Hud Color
restart
lbsize
gamma 
saturation Saturation
mousescale Mouse Scale
huddetail
tracers
netdelay 
talkred
talkblue
resetgames 
Ban
LastGame 
fly_down
center_view
fly_up
toggle_item
look_up_abs 
look_dn_abs
turn_left_abs
turn_right_abs
briefing
command
PrintScreen
scope
SaveGame
LoadGame
CrossHairColor 
lockgame
help
server
showgun
escape
NextWaypoint
Drop
Pause
Binoculars
BigMap
OldMessages
ShowFriendly
MissionGoals
NextFlag
AudioMacros
NVG
CoolNVG
0tossslot
stalk
talk
killlist
VonTalk
VonSLT
VonDLT
VonDisplay 
VonUSP
VonRVU
VonRVD
VonMCT
VonBT
VonSBX
1knife
2sidearm
3primary_weapon Primary WPN
4second_weapon
5explosives
6detonator
7grenade
8laser
9medic
magazine
cycle
scopeinc
scopedec
scopemag
setasslot0
setasslot1
setasslot2
setasslot3
setasslot4
setasslot5
setasslot6
setasslot7
setasslot8
setasslot9
attack_1
move_back
move_forward
slide_left
slide_right
alt_move_back
alt_move_forward Forward
move_jump
look_down
look_up
alt_slide_left
alt_slide_right
turn_left
turn_right
NoRun
Slide
Crouch
Prone
Stand
zoomin
zoomout
1stPerson
CameraLeft
CameraRight
CameraUp
CameraDown 
CameraZoomIn
CameraZoomOut
drury
kariya
roy
corbet 
domi Artilary Strikes