Regirock

Regirock sports an amazingly high base 200 Defense, backed by an acceptable base 80 HP. It can take on some of the strongest physical attacks, even weaker super effective ones. Additionally, Regirock can make do with its base 100 Special Defense with EV investment while still maintaining most of its physical bulk. Rock is not an excellent defensive typing as it's weak to many common attacking types, such as Ground, Water, Grass, and Fighting; nonetheless, it grants Regirock a crucial resistance to Fire, which allows it to comfortably check many Fire-types, such as Moltres and Entei. Another of Regirock's flaws is its lack of any reliable recovery outside of Rest. Despite such drawbacks, Regirock is still a very sturdy and reliable defensive Pokemon in RU, and also one that can set Stealth Rock reliably and repeatedly when needed. Aside from being a generally good bulky wall to fall back on, Regirock finds its niche in stopping many Fire-types--specifically, it is one of the few counters to Moltres.