Formula Synchron seems like a good card at first but it is simply amazing when it comes to actual Duels. Plants and are known for Synchro Summoning with small Level Tuners like Glow-Up Bulb and Tokens as the Non-Tuners. So the Plant Duelist instead of Synchroing Glow-Up Bulb and a Dandylion Token and a Reborn Tengu for Brionac, Dragon of the Ice Barrier, he can simply tune Bulb and Token for Formula drawing one card and then Synchro for Brionac while also fueling the Grave with cards for Pot of Avarice. With the arrival of T.G. Hyper Librarian this card's summon means an instant Pot of Greed with Librarian in the field and this is the primary reason it could not be left in Unlimited Status.
|Number 5: Formula Synchron|
But when Formula was at Unlimited Status along with Fishborg Blaster he used to shine in Frog Monarchs and Fish Synchro OTK Decks. This is because he used to nullify both drawbacks of Fishborg Blaster by Synhcro Fishborg Blaster and Treeborn Frog into Formula, drawing one card (so it made up for the cost of discarding) and then you can use Formula to Synchro into anything (bypassing the Water-Only Non-Tuners restriction of Fishborg Blaster). This gave some speed to both the aforementioned Decks but particularly in Fish Synchro it used to help a lot during the "Big Turn" Synchro Shenanigans by enabling the Summon of Monsters like Red Nova Dragon.
But Formula is also a Synchro Tuner and this means two things. First he can be used to Summon big guys like Shooting Star Dragon and Shooting Quasar Dragon and second he can be used for a Synchro Summon in the opponent's turn. This can be used to devastate the opponent's field with Black Rose Dragon or chain the Summon of T.G Hyper Librarian at the opponent's Synchro Summon to draw some cards or Summon Trishula to devastate the opponent at the time he is most vulnerable.
All in all Formula Synchron is a nasty little Synchro with much more impact to the Metagame than expected definately deserving the 5th Spot to this Countdown. Some may say the it is even higer but the cards here on are all Bosses tha win games while Formula has a support role and not a game-winning one.