Here are my own ideas. I’d love to hear your thoughts on them before posting your own. 
Assault Rifle
The AR is already near perfect. It’s not a very original design, but we know it will work. 
I love the tall CE-esque ammo counter, and I’m sure the weapon will look great once it’s fully textured.
Sidekick (Pistol)
This one is easy. Shrink it down. Add the green lights and the little red rectangle, and then it’s done.
Commando
Slap the ammo counter on top of the weapon and change the display to blue. Move the holographic sight further down the weapon behind the ammo counter. Darken the weapon and add a single stripe, any colour other than the white already used on the assault rifle. The weapon still wouldn’t be completely unique, but it would look that bit more like a Halo weapon and its silhouette would be slightly more distinct with the ammo counter and sight in separate sections at the top.
Bulldog (Auto-Shotgun)
Honestly, a little goes a long way with this one. The design is mostly fine, but it’s missing one vital element: Halo’s shotgun sights. Slap on some yellow sights to contrast the standard shotgun’s cyan coloured ones. Keep the shapes of the sights between the two shotguns similar but not the same. Everything else about the Bulldog is fine. It really needs those Halo sights.
Mangler
Okay. This entire weapon needs to change! Get rid of all the right angles. There should be no right angles on a Jiralhanae weapon. Curve the front blades forward. Make them look sharp and dangerous. Add scratches and plenty or dirt over the weapon. Swap the red bullets out for glowing red lights (even if there are still technically bullets inside). Make the cylinder larger with grooves similar to the Mauler.
Ravager
This entire design needs to change as well. Keep the large baronet, but change the shape of the body. Give it three metal segments, kind of rounded but with very rough joints. Think of the Banished base or lich from Halo Wars 2. The rounded-ness of the weapon hints at its plasma fire, but everything else spells ‘Brute’.
Pulse Rifle
Smoothen and round out this Elite weapon in order for it to not look so human. The purple parts should blend more seamlessly into the barrel. Think classic carbine crossed with the classic plasma rifle. The purple should be much more vibrant but still purple to keep it different from the blue plasma rifle that should still be present in the game. Replace the front gauge with an alien symbol on the side, similar but different from the plasma rifle’s side gauge.
Needler
I would make this weapon look a little more Banished. Change the colour scheme of its shell to silver and red. If not, just give us something a little more original than the Halo 4 design we’ve seen in the screenshots. I’m a little tired of seeing this exact same needler over and over, especially when the needler in Halo 5 was one of the designs I welcomed.
Plasma Pistol
Get rid of the Halo 5 design. Go with something more recognisable / classic. Change the shell to silver and red but make the green highlights glow a little more.
Please share your thoughts on these weapons as they currently exist in Infinite. Do you agree with these fixes? What would you do to improve each of the weapons we’ve seen in Infinite so far? Your changes don’t only have to be aesthetic like mine. You can include any gameplay or audio issues you’d like fixed as well (or instead). I would love to hear your thoughts and ideas!