It's a difficult question, but if you can only name one class.
Which class do you think best fits an Orc?
Remember, there is no correct answer, only true feelings.
Might as well mention some iconic Orc characters here:
Thrall, Shaman
Garrosh, Warrior
Gul'dan, Warlock
Ner'zhul, Shaman
Nazgrim, Warrior