D-Pad directions are the selectors for equipping a frag, plasma, Power Grenade or Equipment. Pressing the throw grenade button will throw which ever item you have selected.
Power Cores are ammunition for Power Grenades and Equipment but could be used to temporarily modify a weapon too.
Power Cores are dropped from Spartan corpses.
Power Grenades are items found on the map, never spawned with. Power Grenades are unique and powerful grenades that serve a more specific purpose than a frag or plasma. Power grenades are selected by pressing Up on the D-Pad.
Equipment is items similar to some equipment from Halo 3 as well as some new gadgets. You can hold one Power Grenade and one Equipment at a time. One of each type only, not two of one type. Equipment is selected by pressing Down on the D-Pad.
Power cores can act as modifiers for weapons. Holding B causes you to insert the Power Core into the weapon you are currently holding.
Performing an Assassination would automatically give you the Power Cores that your victim was holding.
Power cores will be easy to spot laying on the battlefield. They will be explosive while laying on the ground so shooting a Power Core a few times or throwing a grenade at a Power Core will cause it to explode. Power Cores become random map hazards that benefit the player who takes the risk to pick them up.
Gameplay would change over the course of the game as players attempt to gain their Power Grenade / Equipment of choice and the appropriate number of Power Cores to make it function.
All Power Cores, Equipment and Power Grenades are lost when you die. Whether or not you drop them onto the battle field for others to pick up could be a configurable option. The number of Power Cores it takes to make Power Grenades / Equipment function could be adjusted. The number of Power Cores to modify your weapon could be adjusted. Power Cores could be disabled entirely making Power Grenades / Equipment function as soon as they are picked up from the battle field. Pressing B to pick up Power Cores could be disabled to allow the player to automatically pick them up as he walks over them. The maximum number of Power Cores a player can carry at any one time could be adjusted.
Loadouts could be an option for custom games. You could let people choose their class which could include Power Grenades or Equipment off spawn.