Slowbro
Slowbro is already a very tanky pokemon and having an armor would be beneficial because it could raise its defenses a lot and gain hp with slack off and regenerator.
Luxray
Luxray tends to be more of an offensive pokemon so instead of a life orb to easily wear itself down it can do the reverse and keep a lot of its hp. The only drawback to a luxray armor is when luxray uses wild charge.
Kabutops
Kabutops is found at the scientists club in Koril Town, giving it armor would greatly increase its usage, its high attack and armor covers for its frail defenses, which like luxray, can use the armor effectively.
Nidoking, Nidoqueen
Nidoking and Nidoqueen both have decent defenses which can then be used in a bulky offense set. This could get Nidoking back into the ou tier.
Swampert
Swampert is a very bulky pokemon and if used correctly, can also deal high amounts of damage. Mega swampert should be used if the team is overall offensive, but if swampert had armor it would really shine its defensive attributes.
Garchomp
Like flygon, garchomp is also a dragon-ground type, and is commonly used in the ou tier as a tank. Armor could help garchomp by not only raising it’s defenses but also allowing it to use moves like outrage more commonly because it could not worry about getting revenge-killed that easily.
Hippowdon
Already being extremely tanky, hippowdon uses weather to deal more damage and recieve less. Now when armor is combined with theses defenses, hippowdon becomes so tanky it may even be moved up to ubers.
Toxicroak
Toxicroak is a very under-used pokemon, that has a lot of potential. With dry skin and armor a combo of toxicroak and ferrothorn under rain could be exremely dangerous.
Magmortar
With flame body already, magmortar can use the armor to maintain hp and punish as many physical attackers as it can.
Electivire
Electivire is another very great pokemon to pair with armor, having motor drive and a wide movepool means it can be a serious threat to many teams.
Delta Scizor
Delta scizor needs armor because if you have a bulky offensive set (like I do) then you can bump up its defensive stats a lot and make it more of a threat than it already is.
Haxorus
Haxorus has an insanely high attack with very moderate defenses, an armor for it could make it a seriously strong tank if it has dragon dance.
Hydreigon
Hydreigon is a very powerful pokemon. Like haxorus, it doesn’t have good enough defenses especially because of its 4x weakness to fighting. An armor will help it last longer on the field since it is typically a hit and go pokemon due to draco meteor.
tyrantrum, trevenant, delta bisharp, delta snorlax