In order to activate a console command, open the console by pressing the Enter key on the numeric keypad, then type the command, then press Esc to quit the console.

ammo - Infinite ammo
autolose - Does what it says
autowin - Finished the level
badtree - This command highlights trees that have been placed too close together, and they might cause AI errors, by setting them on fire!
bc3000ad- crashes PC? Possible in reference to Battle Cruiser 3000 - a very buggy game.
boom - Makes the world shake once
chickenrun - Turn gernade's into chickens which have a delay before they explode
cisco - Wins with a dog bark (maybe more), achieves objectives one at a time
eviltwin - Makes everyone look funny
extremepaintball - seems to turn AI off. Enemies that are on patrol will keep walking in the same direction, even if there are walls and whatnot in the way.
god - Get struck down. Throws you in the air - you hit the ground and die in a flame!
help - Shows all commands/cheats
hidecorpse - Does what it says
hidegamecounter - Does what it says
journalplaystart - Starts playing of record
journalplaystop - Stops playing of record
journalrecordstart - Starts recording of game
journalrecordstop - Stops recording of game
listcmds - Same as help
listtypes - Does what it says
listvars - Does what it says
loc - Shows current location
mark - Marks your current position
mark2 - Marks your current position
names - Shows names of everyone in the game no matter where they are
perf - Shows a lot of stats
quit - Quit's the whole game
range - Shows range of people when you move your mouse over them
refill - Refill ammo
reticule - When you put your reticule over a person or object (including doors, cars, tanks), it shows the name of the item and how far it is away
rock - All your base's are belong to us
rumbleon/rumbleoff - Earthquake mode on/off
run - Makes you walk fast and run even faster, by a factor of 10
setgama ### - Set's the gama level (replace ### with numbers)
shadow - Can't see controlled player - invisibilty
showframecounter - Does what it says
showgamecounter - Does what it says
showmotions - Kind of works like a giant sensor, just not as good
squirrelkite - Turns grenad's to squirrels - shoot at the trees and see flying squirrels
superman - Controlled player can't die - invincible
teamshadow - Can't see team - invisibility
teamsuperman - Team can't die
teleport - Teleport to mark
toggleAi - Toggle's AI
togglemovetrees - Makes tree stands still
toggleshowframerate - shows framerate during game
unlockhero - Unlocks the hero for the current mission

Unkown effects
aiinfo
airoe
alias
cover
coverpoints
dist
echo
exec
findcover
kit
levelmaps
loadgame
modelupdate
pathpointlines
pathpoint
rem
report
savegame
setalert
setgama
showfacing
showguns
testpath
toggleshowactorcharacterstats
toggleshoweffectsstats
toggleshowinter
toggleshowlevelstats
toggleshowperfcounters
toggleshowscenestats
toggleshowsystemmemorystats
toggleshowtexturememorystats
toggletotalstats
toggleUI
toggleusesimhumaninterlevel
toggleusetreeinterlevel