Today we'll look at an easily disregarded and underestimated common from Photon Shockwave.
Sound the Retreat!
Return all monsters you control to the hand.
Now at first appearance why would anyone run this? After all the hard work you did to get a few monsters on the field why put yourself back to square one? Some people use Compulsory Evacuation Device in response to the opp's removal effect to save their monster. This would do it largescale in response to mass removal like Dark Hole and the freshly semi limited Torrential Tribute. But then you'd have to summon them all over again.
Now here comes the ingeniousness someone brought up on Pojo the other day about the card. Use Magical Hats.
Activate only during your opponent's Battle Phase. Select 2 non-Monster Cards from your Deck and 1 monster you control. Shuffle those 3 cards and Set them on the field in facedown Defense Position. The 2 cards selected from your Deck are treated as monsters (ATK 0/DEF 0) and are destroyed at the end of the Battle Phase.
A favorite of Yugi's, this card has seen play a few times, largely in Geartown decks. Grab a pair of Geartown, make your opp choose either to atk em or end the battle phase and out pops Ancient Gear Gadjiltron Dragons.
Now with Sound the Retreat we have an instant Gold Sarcophagus that'll net you 2 spell/trap cards.
As with most combo decks, this one will need the help of Pot of Duality. The only issue is that these cards take up almost a quarter of the deck if you use em in full quantities. Try out different numbers on DN and see what works for you. Aside from this being a rather ingenious engine the deck can be anything you'd like.