If your opponent destroys "Giant Rat" in battle with a monster that will Special Summon another monster, such as "Blackwing - Shura of the Azure Flame", "Shining Angel", etc., your "Giant Rat" will be Chain Link 2 due to game mechanics; take advantage of this and Special Summon this card to stop your opponent's strategy.
This card can be combined with "Creature Swap". They'll have a very difficult time getting rid of it on their own field unless a "Monarch" Deck is used. Just Set a monster with high DEF and your opponent will be locked down for potentially the whole game.
Add "Mask of Restrict" to this to make it, so that your opponent can't just Tribute this card to get rid of it.
Cards like "Shrink" or "Forbidden Lance" can also be used to protect it from your opponent's monsters while also destroying them in battle, leaving your opponent open to direct attacks later.
Use this card in a Deck with "Morphing Jar #2". If the opponent flips up "Morphing Jar #2" by battle, it can Special Summon several monsters to your and your opponent`s field, effectively ending their Battle Phase. During your turn, this card can be Flip Summoned to destroy all monsters Special Summoned this way to clear the field and still have your Normal Summon to attack directly.
This card works really well with "The Seal of Orichalcos" if there is a another monster on the field of the same or higher ATK.