Various Cheats:
First, hit "enter" on the Num Pad. Then type in any of the following cheats:

Shadow----- Invisible
TeamShadow-- Team Invisible
Superman---- God
TeamSuperman--- Team God
Ammo----- Unlimited Ammo
Refill----- Refill ammo
UnlockHeros--- Unlock all heros
autowin---- Finished the level
chickenrun - Get chickens from grenades
god - Get struck down

Unlock all Missions!:
In the main Ghost Recon Directory there is a XML document named unlocked_missions.xml and inside this file it lists all the missions you have unlocked. All you have to do is open the source code, erase everything and enter the following text:

<UnlockedMissions>
<Mission>m01_caves.mis</Mission>
<Mission>m02_farm.mis</Mission>
<Mission>m03_rrbridge.mis</Mission>
<Mission>m04_village.mis</Mission>
<Mission>m05_embassy.mis</Mission>
<Mission>m06_castle.mis</Mission>
<Mission>m07_river.mis</Mission>
<Mission>m08_battlefield.mis</Mission>
<Mission>m09_swamp.mis</Mission>
<Mission>m10_ruined_city.mis</Mission>
<Mission>m11_pow_camp.mis</Mission>
<Mission>m12_docks.mis</Mission>
<Mission>m13_airbase.mis</Mission>
<Mission>m14_mountain.mis</Mission>
<Mission>m15_red_square.mis</Mission>
</UnlockedMissions>

Save this file as the original file name (unlocked_missions.xml) in the same directory and THERE! You can now access all the unlocked missions!