Nitron 100% covered it. However, it bares repeating: - Ammo is divided into 3 all-purpose (color-coded) categories that correspond to the weapon slots. So you have Primary, Special, and Heavy ammo. - Instead of weapons spawning on the map, like they do in Halo, you have ammo-drops/ammo-crates. So Destiny is still about map control. If you want Heavy ammo, you have to go find it [i]or[/i] control the area where it is found. - You spawn with no heavy ammo and, when you die, you drop all your ammo. - To add an additional layer of skill to Heavy Weapons, when you do finally track down Heavy ammo, you have to first reload your weapon before you can fire it. - Primary weapon ammo count resets when you respawn. No official word on the Special weapon slot. - Ammo itself has no perks or upgrade trees. Ammo is upgraded through the weapons themselves. The reason for this is sandbox balancing. This generic ammo type system was created to make it easier on designers and give them more freedom. We learned 90% of this information in the podcast from September 2013. The last 10% from the Dec/Jan Game Informer 14-page article and the January 2014 Podcast: September 24th, Bungie Podcast: http://www.bungie.net/en/News/News?aid=11100 Discussion of Weapon Slots, 37mins. Discussion of Ammo Types, 47mins. Game Informer Destiny Article: http://ge.tt/4QJpll81/v/0

[quote]Will they provide just a damage boost[/quote]Yes, in that they allow your gun to fire, without which your damage output is zero.[quote]or unique effects that add (even more) variety to gameplay?[/quote]All evidence points to your weapon having special effects, not the ammo. [quote]When firing Heavy Ammo, will there be a downside to balance this increase in firepower[/quote]Your heavy weapon is meant to be a powerful weapon, it's balanced by the scarcity of heavy ammo. [quote]or will the differences be minimal?[/quote]We don't know specific weapon damage stats. [quote]How will be able to tell when someone is using a different ammo type?[/quote]There are only three types. It will be clear based on the weapon.