Having now covered two races within my world, I wanted to take a moment and look at how the orcs fit into the eleven classes within the Player's Handbook.
This is the favoured class of orcs. The barbarian class plays to the strengths of the race; quite literally their increased physical strength. Their ferocious nature, toughness and often reckless nature meshes quite neatly with how a barbarian usually works.
Orc bards are uncommon, but not unheard of. Their low intellect often makes them struggle with lore and fact-finding, but their oral tradition is noted, and frequently orc bards have composed evocative poems, sagas and even ballads. Orc performers in larger settlements will often grab attention as something of a novelty, but prove they have the ability to go with it. Orc music often uses horns, drums and bone flutes.
Orc clerics are often worshippers of Gruumsh or D'zl. Those who follow Gruumsh merit strength and battle prowess above all else, frequently using spells to improve those qualities in themselves and their allies. D'zl priests are often direct and destructive, utilising spells that manipulate fire as often as possible. Orcs are unlike to follow a more scholarly path as clerics, owing to the clerics place in society as spiritual leaders, which frequently dictates a much more hands on role.
The history of the orcs as being tribal nomads in the wilderness means that few are surprised by the existence of orc druids. True survivors, orc druids can survive out in the wilds for great lengths of time and make excellent scouts, scavengers and hunters.
Almost as popular and common as orc barbarians is the orc fighter, marrying physical strength with skill-at-arms, instead of unbridled rage. An orc's training with the "double axe" opens up a number of options for orc fighters to pursue, as well as taking advantage of their strength.
Monastic orcs are a rare sight, owing to the race's tendency towards chaos, but the odd few find themselves drawn to the monk's path of physical perfection and self-sufficiency. While they may struggle with the discipline, orcs often find the rigours of the ascetic lifestyle easier to adopt owing to their wilderness origins.
Similarly, orcs are rarely paladins, as they chafe under the strict code. That said, some find glory and honour (something many orcs desire) in taking up the mantle and seeking to prove themselves stronger than evil. While many orders will think twice before recruiting an orc, those who accept them learn the value of having a strong, determined adherent like an orc.
The orcs' background means that the ranger's path isn't a stretch of the imagination; combat prowess, minor magics and survivalist skills are all things that would serve a wandering orc tribe well. Many orc rangers favour the use of the two weapon fighting style, often using their race's signature weapon, and surprising many foes who just assume them to be simple warriors using a weapon that seems unwieldy.
The biggest obstacle for an orc as a rogue is their relatively limited intellect; limiting how skilful they can be, and limiting how effective some of their skills will be (such as disabling traps). Conversely, it is this very challenge that makes orc rogues effective; nobody expects these hulking savages to be stealthy or cunning.
Few expect orcs to wield arcane powers, but the innate power of the sorcerer can occur in almost any race, and orcs are no exception. They often favour spells that are destructive and/or enhance their already prodigous strength. With the right training, an orc "battle sorcerer" could be a fearsome opponent indeed.
Few orcs are capable of reading or writing, and most struggle with some of the more basic aspects of scholastic pursuits. Taking on the life of a wizard is a huge challenge for an orc, as they need a focused, orderly mind and a capacity for reason and study that many of them lack. The few that overcome this shortcoming find they're often underestimated in how much of a threat they are; similar to rogues and sorcerers.