There are three types, in my eyes, that are so fucking lackluster and so boring to use. I personally am not a fan of Bug Types (yes they can be cool, but I'm a Misty-person...bugs are disgusting and I hate them) or Normal Types (they serve 0 purpose in battling), HOWEVER above and beyond, the WORST TYPE ON THE POKE-EARTH IS Ground.
They are just a lesser-cool Rock Type, but when has anyone ever specifically wanted to have a ground type on their team? All the good Pokemon with ground typing have another typing which makes them cooler/useful, but having that ground typing gives them so many unnecessary weaknesses.
