Sometimes some classes fit thematically very well a bunch of races (ex: Shaman Orc, Tauren, troll), some other times classes eel kinda wrong for their races (ex. Paladin Taurens ... sigh). SOme other times tho, you can find an odd combination of class spec and race that it's kinda cool while still not looking ridicolous Im gonna put a list here explaining why. Hope you do the same!
Undead Monk (all specs):
the idea of a monk that was dead someway or another and risen again from the dead it's jsut strong. i like it, zombie monks tw
Tauren and Dwarves Brewmaster Monks:
The massive figure of Taurens spitting fire, and the famous affinity of dwarves with beer make this a must.
Pandaren Sublety Rogue:
When you think of Pandarens you don't really think about being a shady guys with daggers, BUT they demonstrated incredible agility already, and jumping in and out of the shadows at high speed make this a perfect "odd" match.
Orc Mage:
I just like it. Especially having like an old, wise orc mage.
Goblin Warrior:
Why Goblin and not gnomes? Goblin are more vicious and ruthless, and honestly they don't feel pity at all. I you think about it they are very good Warriors.
Worgen Death Knight:
It's just badass as f.
Undead Hunter:
Same things as for the monk. Not to mention there are an icnredible amount of "undead" pets, and undead looking weapons and armor to fit this thing even more.
Troll Druid:
Well, this is pretty established by now, but back when Cata was released it kinda got everyone by surprise. I think overall that iit was the most successful race/class combination added there, and they show us a side of druidism never seen before.
Dwarf Warlock:
You know when during the game you encounter those shady maniacs Dwarves that summon strange magics?. Those.