I'm gonna put forward Steely Spirit. Perrserker, the sole owner of the ability, chooses to run Tough Claws over it despite the incredible boost it gives to its STAB moves. However, when combined with the 1.2x boost from our form changing item, the power we can dish out through our Steel moves can become extremely threatening (2x STAB * 1.5x Steely Spirit * 1.2x Item = 3.6 boost). This helps out our offensive ability significantly since Steel hits most viable pokemon in the tier neutrally or resisted.