Dog.

This deck started out as a joke deck with roughly 37 dog-themed monster cards and 3 Where Arf Thou?'s. Since then, it's evolved to be a legitimately playable deck outside of the current meta. Now, the deck is built around using Flamvell Firedog's effect to special summon other fire monsters with under 200 DEF, these mainly being the 6* Hazy Flame Cerberus and the 4* Diceclops. XYZ summoning with Diceclops and Firedog allows you access to huge staples, such as Number 39: Utopia and Gagagigo the Risen. Using Firedog's effect to summon Cerberus ends up with an XYZ summon of Gauntlet Launcher instead. (there aren't a lot of dog XYZs.) Where Arf Thou? is still in the deck, mainly used to summon Slacker Magician in one turn using Outstanding Dog Marron as material. This can be done easily with Double Summon.