Spiritomb

Spiritomb is one of only three fully evolved Pokemon in the game with no type weaknesses at all. Its typing gives it handy immunities to Normal-, Fighting-, and Psychic-type attacks, making it a potent spinblocker that can beat almost all of RU's prominent Rapid Spin users with the right set, including Hitmonchan, Kabutops, and Cryogonal. Furthermore, it is one of the only Pokemon that checks some of the most powerful threats in RU, namely Sigilyph, Gallade, and Slowking, and one of the best Pursuit trappers. Its decent mixed attacking stats let it go either physical or special, but they will almost always require a significant boost to be of much use. However, Spiritomb's lack of attacking options and reliable recovery are setbacks that can cause your team to lose momentum. All in all, Spiritomb is a great Pokemon in the RU tier, but not one that immediately threatens your opponent's team.