Skarmory

Since the very beginning of the GSC metagame, Skarmory has proved to be a force to be reckoned with. With an amazing base 140 Defense stat, 9 resistances, 2 immunities, and no physical weaknesses, Skarmory is easily the best physical wall available in GSC. Throw in Skarmory's ability to phaze opponents with Whirlwind and boost its already ridiculous Defense with Curse, and you have an excellent check to top threats such as Snorlax, Marowak, Heracross, Exeggutor, Machamp, Umbreon, Quagsire, and Espeon. In addition, Skarmory's resistance to Normal-type attacks also makes it a good switch-in to most predicted Explosions.

While Skarmory is an amazing physical wall, it lacks the ability to effectively deal with special attacks from most special and mixed attackers, the reason being its measly base 70 Special Defense and poor base 65 HP. Skarmory's movepool is also rather limited; beyond Toxic and Drill Peck, it has little in the way of offense, and is forced to rely upon Rest and Leftovers for healing off damage due to its lack of recovery options. While sleeping, Skarmory will no longer be able to check some threats, such as Belly Drum Snorlax, Marowak, Machamp, and trappers, although others, such as Curse Snorlax, non-Seismic Toss Heracross, and most Exeggutor, still won't be able to get past Skarmory. That said, Skarmory is still an incredible defensive Pokemon that should always be considered when team building, especially when creating a stall-based team. Ignore this bird of steel at your own risk!