During play, press ~ to open the console. Enter BeMyMonkey to enable

cheats. Now enter any of the following at the console:

God                   God Mode 
Invisible             Invisibility 
Loaded                All weapons 
AllAmmo               Full ammo
GodEx(actor)          God Mode for the given actor 
Phoenix               Phoenix Powersuit 
FearMe                Enemy now fears you 
Ghost                 Ghost mode 
Fly                   Fly mode 
Amphibious            Underwater mode 
Walk                  Normal walking mode 
SloMo(#)              Slow motion   
SetJumpZ(#)           Set jump height 
ToggleInfiniteAmmo    Toggle Infinite Ammo 
ToggleReloads         Toggle Reloads 
ToggleInvisibility    Toggle Invisibility 
Teleport              Teleport to spot the player is looking at 
NextLevel             Skip to next level 
Open(mapname)         Open Map x 
ToggleSpeed           Double speed 
SetSpeed(#)           Set player speed 
ChangeSize(#)         Set player size 
Goodies(#,#)          Summon an array of goodies (see below) 
Sum(Item name)        Summon item (see below)
Actors                Full actor list 
GotoActor(Name)       Change location to the given Actor 
Damage(#,Target)      Damage target by the specified amount 
DamageNPCs(#)         Damage NPCs by the specified amount 
SetHealth(#,Target)   Set health to the specified amount for target 
SetMyHealth(#)        Set player health to the specified amount 
HurtMe(#)             Hurt the player by the specified amount    
ManCannon(#)          Damage all visible pawns 
ToggleServos          Toggle animation servos    
ShowTeams             Show player teams 
Difficulty(#)         Change game difficulty 
CheatView(x)          See view from specific actor
ViewSelf              Target camera on player 
ToggleTimeDemo        Enable time demo 
ToggleScoreBoard      Toggle scoreboard 
EnableFreeOrders(0/1) Toggle free orders 
BehindView            Toggle Behind View 
SetParticleDensity(#) Set particle density    
ToggleImpacts         Toggle impacts 
SetWeaponTick(0/1)    Toggle weapon tick code 
SetWeaponFire(0/1)    Toggle weapon firing 
ToggleShowAll         Show all hidden actors 
ToggleShowKPs         Show all keypoints 
ToggleShowNPs         Show all nagivation points 
ToggleRMode           Toggle RMode    
SetEyeHeight          Set player eye height 
KillActor(x)          Kill specified actor 
KillHitActor          Kill actor under crosshair 
KillHitNPC            Kill NPC under crosshair 
KillActiveNPCS        Kill all active NPCS 
KillDormantNPCS       Kill all dormant NPCS 
GibAllNPCS            Gib all NPCs    
GibHitNPC             Gib the NPC under the crosshair 
PO                    Toggle players only 
ToggleFreezeView      Toggle Freeze View 
ToggleHUD             Toggle HUD 
SetCameraDist(#)      Set camera distance    
FreeCamera(0/1)       Toggle free camera movement 

Item names:

Use these with the ‘Sum’ code above.

ammoAssaultRifle
ammoEnergyRifle
ammoFlameThrower
ammoGrenadeConcussion
ammoGrenadeEMP
ammoGrenadeFragment
ammoGrenadeIncendiary
ammoGrenadeToxic
ammoLaserRifle
ammoPistol
ammoRocketLauncher
ammoShotgun
ammoSmokeGrenade
AutoTurretPickup
FieldGeneratorPickup
ProximitySensorPickup
RocketTurretPickup
weaponAssaultRifle
weaponEnergyRifle
weaponFlameThrower
weaponGrenadeLauncher
weaponLaserRifle
weaponLeechGun
weaponPistol
weaponRocketLauncher
weaponShotgun
weaponSingularityCannon
weaponSniperRifle
weaponTakkra 

Thanks to Revolution readers *FMJ*Firebird and backudog!