Ah Sirfetch'd, this fabled evolution of Farfetch'd, a Pikablu for a new generation. Sirfetch'd has breathed new life into everyone's unfortunate duck (and that face LOL). While most of Sirfetch'd's stats are lackluster, a massive Base 135 ATK is hard to ignore, and a great move pool means few targets can switch in safely. While Sirfetch'd needs a lot of support, it is not unreasonable and once Sirfetch'd gets in safely, one of your opponent's pokémon will fall.
A Knight's Soul
Sirfetch'd
Ability: Scrappy
Item: Leek
-Close Combat
-Leaf Blade
-Night Slash
-Poison Jab/First Impression/Focus Energy
Nature: Jolly (+SPE, -SATK) OR Brave (+ATK, -SPE)
EVs: 4 HP/252 ATK/252 SPE OR 252 HP/252 ATK/4 SDEF
...Is in his weapon. Farfetch'd's signature item, the Leek also works for Sirfetch'd, boosting all attacks to a 50% crit rate, guaranteeing crits after a Focus Energy or a high crit chance move. Due to how crits work, the overall damage is similar to a Choice Band:
252 Atk Sirfetch'd Close Combat vs. 252 HP / 24 Def Ferrothorn on a critical hit: 474-558 (134.6 - 158.5%) -- guaranteed OHKO
252 Atk Choice Band Sirfetch'd Close Combat vs. 252 HP / 24 Def Ferrothorn: 470-554 (133.5 - 157.3%) -- guaranteed OHKO
This has the added benefit of ignoring Attack Drops from outside sources and enables Sirfetch'd to switch around its moves, but requires either setup or luck for Sirfetch'd STABs, as none of them have naturally high crit rates. Close Combat is for STAB, Leaf Blade and Night Slash are naturally high Crit Rate moves that offer good coverage. Last move is up for preference. Poison Jab and First Impression hit Fairies and are a high power Priority move respectively. Focus Energy synergizes well with Leek for guaranteed Crits.