>>46514961Perish song, lowish speed, lack of a 4x weakness and decent bulk give it a niche on perishtrap teams in doubles. Decent special attack and decent coverage options a lot of water types don't get like psychic and earth power make it nice as an offensive weather setter too. Helping hand is also useful in doubles. In most cases, especially in singles, Pelipper is preferable, but Politoed has its uses.
Now if we want to discuss truly cucked weather setters, Gigalith is outdone by Tyranitar in almost every way, and only shines in formats where tyranitar isn't available. Its lower speed makes trick room appealing and having less weaknesses is nice, but tyranitar makes good use of trick room while also being fine outside of it. The dark type is incredibly handy on tyranitar, and ttar's usable special attack and far better special and physical coverage make it a much more versitale attacker. Gigalith has at best similar and more often worse stats than Tyranitar too. If Gigalith was a special attacker with better coverage it'd probably have a decent niche, but as it stands Tyranitar outclasses it.