Skarmory

Skarmory is among the premier Steel-types of Ubers for a reason. It has a key Dragon resistance that gives it the ability to check many common Pokemon such as Rayquaza and Groudon that lack Overheat. It's also got a quadruple Grass resistance and a resistance to Flying-type attacks, making Skarmory one of the best Shaymin-S checks around. Additionally, Skarmory is a hard stop to Scizor, as well as Latios and Latias that lack Thunder, Surf, and Hidden Power Fire. Setting up Spikes is a niche for which it competes with Forretress, but Skarmory is arguably better at it thanks to its access to Taunt. The combination of Taunt and Spikes makes Skarmory a decent lead, checking Groudon without a Fire-type attack and Deoxys-S to boot. Regardless of these positive attributes, Forretress is used more because it also has access to Toxic Spikes and Rapid Spin. However, Skarmory is still a great Pokemon as it has its niches over its competition that make it a solid choice.