An especially great card to equip this to is "Victory Viper XX03", as its effect summons more Token Monsters, and each token summoned by the card always has the same ATK and DEF. The first token summoned will have 2800 ATK if you have no other monsters apart from "Victory Viper XX03" It is a perfect way to gain the benefits of the monster count.
During the same turn, if the monster is equipped with this card, be sure to activate "Scapegoat" at the legal timing, so the, there will be 5 monsters on the same side and the equipped monster gains 4000 ATK. Also, for extra safety, equipping "Raregold Armor" on the monster that was equipping with this card, so the target monster would always be attacked by the opponent monster(s). The best choice of monsters for this combo are: "Five-Headed Dragon", "Hayabusa Knight" and "Mataza the Zapper".
Try this combo: Summon "Marauding Captain" and use its effect to Special Summon "Hero Kid" and use its effect to summon up to 2 more copies of "Hero Kid". Then equip "Marauding Captain" with "United We Stand" so your opponent has to attack it while it's powered up before they attack any other monsters you control.
Equip this card to "Raging Flame Sprite" to give it an 800 on the first turn it's summoned, and an added 1000 ATK for each time it attacks successfully.
Use this card in a "Frog" Deck, seeing as how Frog monsters are able to swarm the field quickly. This card attached to "Unifrog", for example, with five monsters on the field and "Wetlands" results in a 5600 Direct Attack. Even better, two copies of "United We Stand" equipped to "Unifrog" would result in a 9600 Direct Attack, easily enough to end the Duel in most cases.
Use this card in "Watt" Deck - lock your opponent down with 2 copies of "Watthopper", then equip this card to 1 of your direct attackers. Use "Watthydra" to search your Deck for this card. If you have 2 more "Watt" monsters on your side of the field, your direct attack will grow up to at least 5000.
Use this card with "Mage Power" along with "The A. Forces" in a warrior type deck that swarms the field for a critical attack boost.
Using more than 1 copy of this card will make the attack boost even larger.
Use this card with Link Monsters, as most Link Monsters need to have monsters linked to them to activate their effects, this card can make their ATK much higher from having monsters linked to them