This is a very long explanation as to why I chose everything for my loadout, read if you want. But just read what I use, and plz rate and suggest improvements. I edit my loadouts in-game if I ever do feel that I do need a change. It took me about half an hour to come up with this 
Loadout 2 - Big Team Infinity Slayer
Primary Weapon: DMR, Light Rifle
Secondary Weapon: Plasma Pistol, Boltshot
Grenade: Frag Grenade, Plasma Grenade
Armor Ability: Active Camouflage, Hardlight Shield, Regeneration Field
Tactical Package: AA Efficiency, Requisition, Shielding, Wheelman (with Gunner)
Support Upgrade: Ammo, Awareness, Sensor, Stability, Gunner (with Wheelman)****
Notes: This loadout is specifically designed for Big Team Infinity Slayer, to greatly better your performance.
-The DMR is perfect for nearly every situation, and is one of the best weapons to use as all maps in Big Team Infinity Slayer are quite big. The Light Rifle is also another great choice if you want to hang back and pick off enemies in the open who are on the battlefield, coming at you. Both weapons have great accuracy, scope, and are headshot-capable weapons.
-Are you feeling offended and bothered by a vehicle on the battlefield? Plasma pistols are ridiculous in this game, use the overcharge to EMP and freeze it in it’s tracks and finish the drivers/pilot with a few grenades. Remember that a lot of people choose to spawn with plasma pistols in Halo 4, and side by them to EMP vehicles together. The Boltshot is perfect for very close-range battles, one charged shot will get rid of your enemies in those kind of situations. The Boltshot covers for the weaknesses of the Primary Weapon that you are using.
-Use frag grenades to deal damage, and use plasma grenades to stick vehicles and enemies.
-From a good distance away, your Active Camouflage will render you almost completely invisible to enemies (if you stay still) as it won’t scramble enemies’ radars. Active Camouflage is ideal for stealthy sniping. However, Active Camouflage may not be entirely necessary, as staying still without it can prevent you from popping on enemy radars. Hardlight Shield will give you time to move into cover, but unless you can get a few teammates to finish off your attackers, you will probably die. Regeneration Field must be deployed in cover, to start up the shield recharge fast for you to get back into battle. It will also be of great assistance to your teammates.
-AA Efficiency will help you utilize your armor abilities a lot better and more often. Requisition will give you another chance to get an ordnance drop fit for your current situation. Shielding is best paired with Regeneration Field as your armor ability. Wheelman will work best for you if you plan on making heavy use of vehicles, but if you choose to use Wheelman, pair it with Gunner as the Support Upgrade in your loadout.
-Ammo is ideal for Big Team Infinity Slayer. It’s hard to find ammo for your guns in such big maps. Ammo will help you worry less about running out of ammo obviously, and will give you more time to use power weapons from ordnance drops. This loadout is heavily designed for long-range combat, so Awareness will be a big help, giving you more situational awareness while you’re scoped. Sensor will give you a better picture of the map and affect your decisions on how to navigate it. If you see three enemies and you are all alone, it’s most likely best to skip that fight. Stability is also a very great option, which nicely compliments precision and sniper weapons. Gunner is absolutely beautiful if you’re in control of a firing-position on a Warthog, Banshee, Turret, or Mantis. Use it with Wheelman if you plan on using vehicles a lot.
