On Orcs: Well, there was one for dwarves...

[Seraph]

My settings usually involve much less sexism than the real world, but may not do away with it completely.  The Orc tribes in my setting tend to be more sexist than the rest of the world.  In Camulus orcs, goblins, hobs, and bugbears marry literally just by kidnapping their wives.  They remain married as long as the wife remains with him.  She may or may not try to escape.  Another orc can steal your wife, making her HIS wife instead.  They have no concept of "rape" because they have no concept of "consent" of any kind: if you want something, you take it--if you can.  

On the flip-side, because this society is all about power and what you can do, if an orc woman were to exercise her power in the same way as orc men, she could take multiple captive husbands as well.  But since the men always take the best and the most of the food, and are more practiced in the arts of war, a woman rarely has the chance to gain enough strength and power to do this, and so women end up being viewed as property, even though this is not formally institutionalized.  

In Avayevnon, my "Spartan" orcs have a similar marriage ceremony (kidnapping), but it is a more formalized ritual and less brutish.  

[Cheomesh]

There are no female orcs; everyone knows orcs are the off spring of the Orcen tree, being the things created inside those bulb...things...you see hanging off those vines.

This is a mountain biome tree, which is why you see so many orcs in woodland mountains.

They are so hostile because these "male" orcs are also the primary means of propagation.  The "rape" part of "rape, pillage, plunder" will convert the unfortunate victim into another tree, over the course of months.

The pillage and plunder part is sort of an artifact, though scientists seem to agree it's a form of landscaping - raze places to make a rich, ash-infused soil perfect for the growth of a new Orcen tree. 

They travel in packs because this achieves their goals better.  Kind of like wolves.  Sometimes a few will go solo; these are another survival adaptation to try and propagate new Orcan trees in different areas.

They're not truly sentient, though, so hack and slash away!

M.

[Rhamnousia]

In an introductory Pathfinder campaign I'm working set in what is basically post-glasnost Mordor (if you think that sounds Terry Pratchett-esque, you're spot on), orcs make up a major section of the population. While not created from corrupted elves or anything so Tolkenian (they're closer to the Warcraft end of the spectrum, for those of you who are fans of TVTropes), they have been used as shock troops for the Unholy Empire for the better part of the past thousand years and most of them, as with most races in this setting, are quite enthusiastically evil. However, they do resent the idea that they are inherently cruder or more savage than any other race. Since I'm playing with a lot of deliberate anachronisms, they had their own tribal culture before being enslaved by the forces of darkness, but nowadays they're more likely to congregate in gangs or extended criminal families under the banner of an ancient clan: if I had to make a comparison, tribal marks are a bit like Scottish tartans. They're also very far from sexist, coming from a culture that doesn't consider stomping skulls into blood-jelly a gendered action.

Also, half-orcs (or half-humans, depending on who you ask) aren't all the products of rape like virtually every fantasy setting depicts them, because I find it even more unbelievable that no one would want to consensually miscegenate with a tall, strapping warrior just because their faces aren't too conventionally attractive.