I have two loadouts that i mostly use (although i havnt played enough recently to know how if they are efficiant compaired to others) 
  
NAME: The Spearheader 
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Primary: BR 
  
Secondary: Magnum 
  
Grenade: Frag 
  
Aromor Ability: Regen Field 
  
Tactical Package: Explosives 
  
Support Upgrade: Grenades 
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this is my usual loadout, weather im sticking with the team, fighting on my own, or stupidly charging 4v1, this is flexible enough to suit all my need. "I dont always play halo 4, but when I do, I use this." 
  
Name: The Surprise Suppressor-To-The-Face 
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Primary: Carbine 
  
Secondary: Suppressor 
  
Grenade: Frag 
  
Armor Ability: Hologram 
  
Tactical package: Firepower (duh) 
  
Support Upgrade:Dexterity 
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This class i use for smaller maps, even though the carbine is a bit better at range than the BR... anyway, I can take on anyone at range with my Carbine, and swich to my Suppressor (underestimated weapon IMO) if they get in too close. 
  
let me know what you guys think!