Mawile

Despite possessing great defensive typing, an excellent ability in Intimidate, and an undeniable cool factor, Mawile is almost never seen on UU teams. A quick look at its stats will tell you why; its Attack and Defense are average at best, and the rest are terrible. Justifying a spot on your team for Mawile is difficult when other Steel-types with much better stats are available. Luckily, Mawile does have a few tricks up its sleeve that prevent it from being entirely outclassed by Registeel and Aggron, but only in very specific roles. If you're not catering to Mawile's few advantages, you're better off using another Pokemon.