I think that the loadout weapons should have 3 or 4 different ones eg 3/4 UNSC automatics, precision and sidearms, and the same with covey, promethean and maybe return of brute weapons as well.
the snipers could have two variations as well, like the beam rifle and focus rifle for the coveys
here's some ideas:
UNSC:
Shredder - resembles the assault rifle from halo 1 but stockier and shorter
Wrecker - 3 barrels that fire at the same time, mid damage full auto but low fire rate doe slightly higher damage than the BR when all 3 hit
Menace - Precision weapon single fire, high damage but lower fire rate than DMR, longer barrel, accurate but loses it quickly
(un-named) - side arm, 16 rounds full auto, very high fire rate heavily loses accuracy but capable of killing in 12 bullets
Ripper - sniper, 1 round, rail based fire style but can hold the trigger for longer (still limited)
Usable katana - speaks for itself, has own assassinations
COVENANT: (they already have three automatics like the repeater, plasma and storm)
(un-named) - precision, plasma based, flight delay but high shield damage semi auto with a slower fire rate than the carbine
(un-named) - side arm, needle based, 3 needles in soft flesh (shield needs to be down) for supercombine but it would take one and a half clips to take down shields.
PROMETHEAN:
Duster - side arm 6 rounds, produces a small flame that gradually drains enemy shields, 5 out of 6 can kill, can be charged like the boltshot but drains entire clip and produces a larger flame that can continue past an enemy and hit those behind up to a certain distance, killing closer ones instantly and heavily damaging others
Line up - crossbow shaped, fires a horizontal line of hard light, deals high damage but high reload time, if the entire line hits a single person they disintegrate
Buzzer - small but heavy classed weapon, one round, launches a ball similar to one from the incinerator cannon but homes, slow flight and easily avoided, instant kill, if hits a surface a large shield depleting explosion forms
Slicer - gauntlet that forms around the arm with a small light blade (similar to the blades on the prometheans) 2 hit kill has its own assassinations
let me know if you like them and if you think of any names for my un-named ones let me know :3
reply your ideas as well, lets see how creative this community is