Maractus. It's not good competitively. It's not even good ingame. It doesn't evolve from or into anything. It doesn't have any notable trivia other than its own obscurity. In its debut generation, Gen V, it is used by only 6 trainers, and I'm pretty sure all are optional (one is Cilan in B2W2, however, which is something). It is in only one location that you don't spend much time in at 10% encounter rate in that generation. Only one trainer uses it in all of Gen 6 and it is an optional battle in the Mauville Food Court, and the only way to get it natively in Gen VI is Friend Safari and Mirage Spots which have tons of more interesting Pokemon. It is entirely absent from Gen VII shy of transfer. And it is so forgettable nobody in this thread has even mentioned it yet. I rest my case.