Magnezone

At first glance, there seems to be little reason to use Magnezone in OU. It's slow, has crippling weaknesses to common attacking types, and faces stiff competition from other, better Electric-type options available, such as Thundurus. However, its signature ability, Magnet Pull, gives it the excellent niche of being able to trap and remove many common Steel-types, making it a good partner for certain sweepers, such as Mega Pinsir and Dragonite. It also has a whopping 11 resistances and one immunity, the most of any Pokemon in the game. However, at the end of the day, Magnezone is still a rather niche option, and it can struggle to be very effective outside of its niche, which is shrinking more and more by the generation.