Well-reputed in the Pokémon franchise for his huge health total, Blissie is a menace as a gym defender. In Pokémon Go, even with the imperfect stats, it sports one of the top stamina stats in the game.
Metagross has long been considered one of Pokémon Go's best steel-types, thanks to its impressive stats and an excellent array of moves. This makes it a natural fit not only as a gym defender but also as a competitor in raids and in various PvP battle leagues.
The original immovable item in the Pokémon series, Snorlax, originally required a Poke Flute in order to awaken. Like the old days of Pokemon Red, Green, and Blue, it's still challenging to remove in Pokemon Go.