Regirock

Regirock's immense physical bulk and useful resistances to Normal-, Flying-, and Poison-type attacks from common Pokemon such as Kangaskhan, Oricorio-E, and Skuntank allow it many opportunities to cripple foes with Toxic or support its teammates by setting up Stealth Rock. Furthermore, given its access to Sunny Day and a useful ability in Sturdy that allows it to set up the move consistently, Regirock is adept in providing support to weather-based sweepers that are dependent on Chlorophyll being activated, making it an essential component of Sunny Day-based teams. Regirock is not without fault, however: its low Speed stat and weakness to ubiquitous Water-, Ground-, Grass-, and Fighting-type coverage moves leave it easily checked by offensive Pokemon like Jellicent, Golurk, Victreebel, and Gurdurr. Additionally, its inherently passive nature as a defensive Stealth Rock setter means that it can be overly reliant on Toxic to deal significant damage to Pokemon that have a type advantage over Regirock like Gastrodon. Regirock's lack of reliable recovery and vulnerability to entry hazards are detrimental to its longevity, which can in turn disallow Regirock to switch into the Pokemon that it is meant to check.