Cloyster

Cloyster is one of the most important Pokemon in GSC Ubers mainly due to its access to Spikes, although it also has other virtues. Spikes gives teammates like Zapdos and offensive Mewtwo some extra help in threatening Pokemon like Snorlax and Raikou. Cloyster excels at providing offensive utility in other ways as well, with its decently strong STAB Surf dealing damage to every Pokemon that resists Normal that would try and pivot into Explosion, namely Tyranitar, Steelix, Golem, and Gengar. Furthermore, Cloyster's access to supportive moves like Toxic, Icy Wind, and potentially Rapid Spin gives it surprising depth in what it can do to support its team.

However, while Cloyster's Defense stat is gigantic, it cannot switch in constantly on physical attackers like Snorlax during longer games. Because of this, it faces direct competition with Forretress, as the latter's Normal resistance and, more importantly, Toxic immunity mean that it can come onto the field with more ease and excel in longer, drawn-out games, whereas Cloyster excels at fast-paced offense. Cloyster's Special Defense is abysmal and, due to it being very common, teams are prepared for it and may run special attacks on their physical attackers, namely Thunder on Mew and sometimes even Snorlax. Lastly, different status conditions like poison and paralysis can force Cloyster to go sooner on the offensive with Explosion, with Cloyster usually trading poison with another Cloyster. This worsens Cloyster's ability to be a mid-game switch-in to Snorlax, Golem, and Tyranitar.