In the vein of things I don't like, and don't want in the games...monks.
I don't like monks. Not because they're Eastern. Eastern is fine. I would happily play in a game based on, say, the battle of Red Cliffs, or one where the fighter was refluffed as a samurai and such.
Why I don't like the monk is because the monk belongs to an entirely different class of storytelling than the other player characters. The fighter and rogue are designed to emulate sword & sorcery, essentially action stories, where the abilities of the protagonists, while improbable, are at least physically possible, if not particularly likely.
Monks belong to a wuxia, kung fu stories, where, if you train long and hard enough, you can balance on a leaf, leap 100 feet through the air, or dodge 100 arrows fired at you at one time. Likewise, if it's possible to slay a dragon naked, with your bare hands if you're skilled enough, what does that say about the skills of someone who needs to be encased in steel and wielding a sword to do the same thing?
In the world of Conan, the greatest of warriors, when armed in a corselet of Shemite steel and wielding an Aquilonion broadsword, can stand against all comers as long as his back is to a wall. In the world of Crouching Tiger Hidden Dragon, the greatest of warriors can fly. To me, that's a difference in storytelling techniques, not character class. Both Li Mu Bayin CTHD and Conan are fighters, if you told Conan's tale as a wuxia story, he would be able to fly too, because that's what great fighters do.
You don't need two character classes "this one trains really hard and becomes a good fighter who is limited by the realities of flesh" and "this one trains really hard and becomes a superhero". You need one class, and two different campaign modules.