my fav is the M1 because its got a powerful single shot like a sniper rifle and if you have a scope i gess it could be used as 1 at a close range its also good for normal close combat. (this is only my expiriance from COD XD)
Sniper, Needler, or Covenant Carbine, because I'm awesome with them... but I'm usually found piloting a Covenant Banshee, unless another player beat me to it.