Come on a ride with two menacing looking guys called Rios and Salem who carry out all sorts of military dirty work for the right price...

When there's something violent, in a rogue state far away, who you gonna call? Err, private military contractors apparently. In EA Montreal's Army of Two, PMCs - as is the acronym - are the concept behind the conflict. The two characters in the game, Tyson Rios and Elliot Salem, are PMCs who work for the highest bidder in warzones across the globe.

So, for example, if Uncle Sam wants to take care of some nasty business abroad but keep their hands clean in the process, guys like Rios and Salem are who they hire. And who wouldn't hire them for such dirty jobs as their military get-up makes them look a little bit like Jason from Friday the 13th (minus chain-saw).

Regardless of the game mode, Rios and Salem are always side by side in this over the shoulder third person shooter. This is because the whole game is built around co-operative play. In order to do this, EA Montreal has devised game sections, gameplay, AI and some very original features which place co-op at the centre of most of your decisions whether you're in a single-player or online game (while there will be online co-op, EA Montreal will neither confirm nor deny any larger multiplayer online games).

The EA Montreal team behind Army of Two took the decision to build it around co-op gameplay because they believe today's shooter market is saturated with conventional single-player titles. Building on the online co-op successes of games such as Gears of War, EA Montreal are hoping that Army of Two will open up the shooter genre to even more co-operative play.

One of the main features in Army of Two, and perhaps the most original as I've never seen anything quite like it, is the aptly named aggrometer. This is basically a sway meter (with each player at either side) that moves towards one side or the other depending on how much heat each player is getting from the enemies. The more heat a player gets, the more they glow red and, once the meter is maxed out, the game goes into overkill mode.

Overkill mode affects both gamers. The one with the most heat goes into a killing spree rage where time slows down and the player has a greater ability to pulverise their adversaries. That guy's team mate goes into a type of stealth mode where they become invisible, allowing them to sneak up on enemies and inflict all kinds of silent pain. Of course, overkill is difficult to reach as gaining the amount of aggro required without dying is a challenge, but it's definitely a great feature tailored specifically for co-op play.

There's also back-to-back mode, which is similar to overkill mode and can be used when you're in a tight spot. Rios and Salem stand back-to-back (as the name suggests) and rotate around each other while letting rip with the munitions. The benefit of back-to-back mode is a bullet-time effect which makes your life much easier, although the pay-off is that both players then become more open to attacks with explosives.

If, or rather when, you have one too many holes made in you by enemy fire and you begin struggling for life, another co-op feature comes into play. Cries of "I'm hit!" and "It's real bad!" should eventually bring your partner to your aid. He'll then start packing you with tampons (yes, you read that right, tampons) to soak up the blood. Apparently, some servicemen told the guys at EA Montreal that they never go into battle without them! Anyway, this forms a mini-game of varied button-pushing as you struggle to save your partners life, or be saved yourself.

But what of the single player game? I hear you ask. Well, the format is the same co-op play as you experience in the multiplayer game. You'll fight alongside either Rios or Salem as an AI partner and here is where it starts to get really clever. The AI will gauge exactly how you're performing. If you're struggling, your AI partner will step-up and take more heat from the enemies. The AI will also respond to the weapons you're using. So, if you're favouring heavy weapons then your partner will strap up with lighter weapons to allow more manoeuvrability. Very literal slaps on the back will be dispensed for good work and a slap on the face for friendly fire. In keeping with this camaraderie styled gameplay, you can direct your AI partner with six different commands: hold position, advance, guard me, build aggro or reduce aggro (hardcore players can even convert these to voice commands via headset).

The demo I saw was a co-op game played over Xbox Live. One great set-piece that showed the gameplay in all its glory was a sniping section where both players had to shoot a fuel canister simultaneously. The bottom half of the screen split in order for you to see both yours and your partner's scope views. It's then a case of one player calling the snipe count down. In single-player games, your AI partner will actually tell you that he's going to call the snipe if your previous sniping accuracy percentage is too low. Another level includes a parachute drop where one player controls the parachute's trajectory, and the other tries to take out RPG laden enemies on the ground.

Army of Two is brimming with original ideas and here's one more great one: EA Montreal have integrated a customisable weapons feature into the game. The more contracts you complete, the more money you receive and the more ridiculous guns you can purchase. Primary, secondary and specialist weapons can all be customised to your heart's desire with noticeable affects in-game. For example, suppressors will reduce the aggro you cause, while shields reduce accuracy but limit damage.