Pretty much weapons from past Halo games + concept art.
Most of the weapons and vehicles are going to be Brutes. I know there’s no brutes in the current Halo universe due to hiding with Prophets and the same goes for jackals and drones not being current. But it’s kind of a celebration thing and whatnot for Halo Wars 2 or maybe the UNSC salvaged / replicated Brute tech.
Brute Shot: Probably as a stand alone weapon that’s a one shot melee and functions more or less like a grenade launcher. If it was added it could probably be a legendary weapon. Maybe as something to celebrate Halo Wars 2 since Brutes are a big focus. Or since it’s name is actually Type-25 Grenade Launcher, it could be a variant of the current Halo 5 grenade launchers.
Missile Pod: Another type of “chaingun” variant you can carry. We have the plasma cannon, chainguns, splinter turret, gauss turret and that’s all I think. I have two ideas for it, a basic variant that just fires rockets like from Halo 3 and another that is similar to the Spnkr EX whereas upon exploding, it lets out smaller explosions instead of exploding like a promethean grenade.
Sticky Detonator: This is just a personal favorite of mine. Same concept as from Halo 4.
Spiker: Pretty much the Brute’s carbine. Same concept as from Halo 3. Maybe variants can be more needler in nature or feature something new.
Mauler: I feel like the concept for Halo 4’s boltshot was like the Mauler, but with a promethean design with two features instead of one. The mauler could be a basic Brute pistol minus the 1 shot + melee combo to instantly kill someone. Maybe the shot can be nerfed to 2 shot + melee to give people an advantage. Or keep it’s combo and up the req level requirements.
Flamethrower: same one from Halo 3, because who doesn’t love them?
Incendiary Grenades: Same as above, why not? It can be similar to the sticky grenade, it’s basically a one-shot grenade, but kills slow enough to allow for a trade.
Now on to the vehicles.
Brute Chopper: one thing I’ve missed since Halo 3 and one thing I’ve hated. It’ll add more fast moving ground vehicles and this could counter things like wraiths and other slow-moving vehicles.
Prowler: Pretty much a Brute warthog. Same concept as from Halo 3.
Spectre: Aside from the ghost and wraith, we lack covenant ground vehicles equal to the UNSC. Maybe bring back the Spectre as a warthog-style ground vehicle.
I don’t have anything on Promethean vehicles / weapons unless something comes from Halo Wars 2.