During gameplay, press ENTER, type in one of the cheats again, then press ENTER again to activate it.

Achieve objectives: cisco
All inventory items: refill
Become invisible: shadow
Change your kit to specified file: kit (kit file)
Chicken grenades: chickenrun
Disable shaky screen: rumbleoff
Don't show corpse names: hidecorpse
Enable shaky screen: rumbleon
Exit game: quit
God mode: superman
Lose mission: autolose
Mark location on map for teleport: mark
Mark location on map for teleport: mark2
Paintball mode: extremepaintball
Report current location: loc
Run: run
Screen shakes: boom
Set gamma: setgama (0.0-1.0)
Show object names: names
Show texture properties for objects: showtextureprops
Squirrel launcher: squirrelkite
Suicide: god
Take over enemy bases: rock
Team God mode: teamsuperman
Team invisibility: teamshadow
Teleport: teleport
Teleport to preset locations: spawn
Toggle AI: toggleai
Toggle display of tracers: tracers
Toggle effect stats: toggleshoweffectsstats
Toggle framerate display: toggleshowframerate
Toggle freezing trees: togglemovetrees
Toggle interface stats: toggleshowinterfacestats
Toggle level stats: toggleshowlevelstats
Toggle performance counters: toggleshowperfcounters
Toggle system memory stats: toggleshowsystemmemorystats
Toggle texture memory stats: toggleshowtexturememorystats
Toggle total stats: toggleshowtotalstats
Toggle user interface: toggleui
Unlimited ammunition: ammo
Unlock Hero characters: unlockheros
View debug counters: perf
Win current mission: autowin

On the last mission called Righteous Archer take out the four towers first. Around the back of the compound (on your map it's the big grey square) there is a helicopter, blow it up with a missile launcher and then continue on with the level. Note: This will not work if you enter the town because he will be alerted and escape.