Hackers have uncovered a number of secret Modern Warfare 2 gameplay modes hidden in the source code.
'Arena', 'Global Thermal Nuclear War', 'One Flag' and 'VIP' have been uncovered, all of which are unfinished and three of which contain the phrase "fix after ship", suggesting that they could eventually be destined for download content.
Raiders Game Net gives us a run down:
"Arena = Round based 1 flag gametype. Basically a flag spawns in the middle, and both teams have to capture it. It's similar to gtnw, except it's the round based (one life) version. A team wins if they capture the flag or kill everyone on the other side.
"GTNW = Global Thermal Nuclear War = Basically the "nuke" is in the middle of the map, and both teams have to try and get it and set it off. It's a respawn gametype. You have to first "capture" the nuke, similar to capturing a flag on domination. If there are more axis players inside the capture zone then allied players, then they will capture the nuke and vice versa. It doesn't speed up the capturing if more players on your team are inside the zone. Once you have 'captured' the nuke - it can only be activated if your team score is above 100. You get 1 point for every enemy you kill, and 1 point each time you "capture" the nuke. So if you go and hold the nuke point, you'll "capture" it, then if you keep control if it, you'll slowly gain more points every few seconds. The team who activates the nuke, wins. If the timelimit is reached, then the team with a higher score wins.
ONEFLAG = Basically round based CTF with 1 flag, so Axis defend while Allies attack. If round time limit is reached the defenders win, if flag is captured the attackers win. If defenders are all killed, attackers win, and if attackers are all killed defenders win. Basically it's like retrieval.
"VIP = Basically it's like assasination. It uses the defenders CTF flag spot as the 'extraction zone' - and picks a random vip... the vip spawns with riot shield and deagle, and also has armor vest and final stand. Once the vip reaches the extraction zone, they have to press use to call in an extraction pickup. This takes 45 seconds, and after that time, the attackers win. The defenders win if they kill the vip or if they kill everyone on the other team. Attackers win if they kill all the defenders, or extract the vip."