Porygon

Porygon's extremely poor stats make it unappealing at first sight, but its access to Recover and Thunder Wave alongside its immunity to Body Slam paralysis gives it a niche. Porygon can switch into the omnipresent Snorlax and use its 32 Recover PP to stall Snorlax out of its 24 Body Slam PP. Non-Amnesia Snorlax sets can only hope to land multiple critical hits in a row or freeze with Ice Beam if Porygon is not carrying Substitute. Porygon can also act as a pseudo-check to other Pokemon unable to reliably status it such as Tauros, Persian, Cloyster, and Gengar, but their higher Speed and likewise higher critical hit rates make switching in a risky proposition.

The biggest issue with Porygon is its passivity. Pokemon like Chansey and Exeggutor take minimal damage and threaten to paralyze Porygon, forcing it to switch out, as paralysis makes it incapable of reliably walling Snorlax. Porygon also struggles heavily against the common Amnesia Snorlax; Porygon can only temporarily stall it with Substitute or attempt to freeze it with Ice Beam. To make things worse, Cloyster gives Porygon strong competition as a more reliable check to Amnesia Snorlax and other Normal-types.