I agree that Skuntank is a fantastic pokemon. Aftermath is one of the best abilities in the game. With Sucker Punch and Aftermath you can put a threatening pokemon in range to where you can set up on them or eliminate it completely. Pokemon like Entei and Braviary (both weak to rocks) rely on their recoil moves to deal the most damage and skuntank's aftermath can effectively cause them to KO themselves.
Its just an excellent emergency answer to a plethora of physical threats. Having steel types take 25% after they take you out is incredibly useful if they're walling certain pokemon on your team. It just opens up your opponent's team and paves the way for something else on your team. It's a team player that does not need a lot of support and helps you retain momentum which is key in pokemon.
Access to taunt and fire blast just allow it to be even more of anti metagame pokemon to handle steels and walls (especially Cress that much better).