Ever since I read the ammo article from Gausswerks (Out of Ammo) I have been giving ammo a lot of thought. Another thing that made me think deeper is how BioWare abandoned it's "infinite ammo" system from Mass Effect 1 in Mass Effect 2.
Quick recap: In ME1 your guns would overheat if you fired them to fast. They work similar to the plasma weapons from the Halo series. So you either had to hold off the trigger and let them cool, or let them vent for a few seconds after overheating. In ME2 they abandoned the system (not in concept though) and use standard ammo clips which run out. Why did they make this choice? I think it's because they realized that ammo adds tension, and tension is good.
What is ammunition in games? It's a way to kill bad guys of course, but in the end it's what keeps you alive. Ammunition is the ultimate realization of "a good offense is the best defense." Imagine you are playing a FPS and you run out of ammo and find yourself in a firefight. You are probably dead. In a case like this, ammo almost acts as a separate life bar. Most well designed games have none-ammo solutions like a knife or a chainsaw but we all know that if you have 0 clips and are forced to use the knife you are pretty much toast especially if you are a hardass playing on the hardest difficulty level. The risk of running out of ammo, which you need to defend your precious life bar, creates tension in your gaming experience. This tension is good. It makes the game more enjoyable because it demands that you as a player make more decisions. You need to choose which gun you use, which ammo to save and when it's safe enough to use the knife. It also pulls you to explore the levels in hopes of finding a hidden ammo stash. I love ammo, and I love being almost out of it.
On interesting innovation in regards to ammo is limiting how many weapons the player can carry. I feel Halo is a pioneer with this concept. It was the first game I ever played that used this limit, Gears of War also adopted the system. It definitely adds more realism and decision making to games. In Doom III you get to keep every gun you find. It's funny to imagine the Doom guy carrying a pistol, machine gun, mini gun, rocket launcher, plasma rifle, BFG, and a chainsaw along with ammo clips for each one. Do you guys even have any idea how much a single rocket would weigh? Well in Halo every time you come across a weapon you need to decide if you want to give up one of your weapons to carry it. Each weapon has unique trade offs. Some are better for little guys, some better for big guys. Some have tons of ammo, others only have a little. The rocket launcher is the ideal example of trade-off. In Doom III once you get the Rocket Launcher you just have it. No matter what the situation you always have it, there is no tension there. In Halo you get a rocket launcher with six rockets and one other gun. The rocket launcher is a very polarized weapon, it is really good sometimes, and really useless other times compared to something like the battle rifle which is pretty good all of the time. Sometimes the rocket launcher will be dead weight and you will wish you didn't decide to lug it around, until the tank comes. But if you didn't take it you will have an easier time fighting all the other stuff until the tank comes. That tension is excellent.
Going more into depth about ammo, I want to talk about the reload. It's something I didn't think about until now. Not all games deal with reloading the same. Wolfenstien and Doom/Doom II back in the old PC days didn't even have a reload button. You had 145 rounds of chain gun ammo and they would magically fly out of your pockets into the barrel of the gun until you were out without a single reload animation. This was very simplistic, and it worked for the time but modern games have a little more realism.
Now you have to reload. Everyone who has played a shooter knows that reloading in the middle of a fight sucks. Deciding when to reload, looking for an opening to reload, and looking for cover to reload in all make the gaming experience more dynamic. It allows more choices for the player, and forces you to adapt to a wider variety of situations. This creates more fun.
One noteworthy game series I wanted to highlight is Bungie's pre-Halo Marathon series. An exceptional shooter with an excellent story and a unique reloading mechanic. In Marathon there is no reload command. All the guns work in clips, but you can't reload until you empty the entire clip. So if you have one bullet left in your eight bullet clip then you just need to shoot that bullet off and insert a new clip. This is much more realistic than how most shooters deal with ammo. They allow you to reload anytime you feel like it. You can hide around the corner, shoot a 3-round burst from your SMG and then while hiding take 3 bullets out of one of the clips you picked up, and insert them into the clip currently in your gun. Of course it's silly to reload partial clips with no consequences, which is why Marathon is so interesting. Playing Marathon presents a deal tension. The risk of running out of ammo is very real, but reloading in the middle of combat also puts you in serious risk. So what do you do when you have three shots left in your pistol, and 2 extra clips on your belt? You will stumble into a battle and be forced to reload after three shots. The only alternative is to just fire off the three shots and totally waste them just so you can be prepared with a new clip. You constantly faced this situation in this game with the pistol, the assault rifle and especially the grenade launcher. I think this element added a lot to the game and I wouldn't mind seeing similar reload mechanic explored in the future.
What am I getting at? Ammunition shouldn't be an afterthought. ME2 is catching a bunch of complaints for adding a "stupid ammo" system. These people are missing the point. ME1 had an ammo system which reduced tension, and decision making. Simply put, in ME1 you never ever ran out of sniper rifle rounds. You never needed to look for or buy more, and you never needed to conserve it or worry about running out. Boring. In ME2, you can carry limited rounds, and need to choose what you snipe. When you are a sniper and run out of sniper rounds, it's as if you are playing a totally different game.
Anyone who doesn't agree is stupid.