Use "Gift of the Martyr" to reduce the number of monsters on your field and give the target Warrior-Type monster an additional power up.
"Rainbow Neos" is probably the best Warrior-Type monster to equip "Assault Armor" to. Once equipped, use its effect to return your opponent's monsters to their Deck and as long as your opponent does not have card effects to stop its attack, Tributing "Assault Armor" will allow "Rainbow Neos" to attack twice. This is an instant OTK since the ATK of "Rainbow Neos" would cause 9000 points of damage.
Combo this card with "Rainbow Neos" and "Hidden Armory" to make an OTK. First, fuse "Rainbow Dragon"/"Rainbow Dark Dragon" with "Elemental HERO Neos" on your hand for "Rainbow Neos". Then equip this card to "Rainbow Neos" and active the effect of "Rainbow Neos" to return all your opponent S/T card to they Deck by sent this card to the Graveyard. After that, active "Hidden Armory" and return this card from your grave to your hand, re-equip it to "Rainbow Neos" and acitve its own effect. Finally, you can allow "Rainbow Neos" to attack twice.
This card can work well with "Nitro Warrior". Because the effect of "Nitro Warrior" it will gain 1000 ATK and "Nitro Warrior" can end up attacking three times because of this Spell. (Once for its regular attack, twice if your opponent has a monster on their side of the field in defense mode, and the third time comes from the extra attack that "Assault Armor" grants.)
This card could be useful in "X-Saber" Decks; many are Warriors, and their effects usually activate when they destroy monsters by battle.
You can do some heavy damage to 2 of your opponent's monsters with this card, "DNA Surgery" set to Warrior, and "Kinetic Soldier".
This card works very well with "Seven Swords Warrior". When equipped, your opponent will lose 800 Life Points and give "Seven Swords" an ATK boost of 300 more ATK to have "Seven Swords" at 2600 ATK. If that isn't enough, you can use a powerful combo by sending "Assault Armor" to the Graveyard and allowing "Seven Swords" to destroy a face-up monster your opponent controls and to attack twice.