Halo 5: Guardians is rated T, unlike pretty much every other Halo

Halo 5: Guardians is rated "T for Teen" by the ESRB. That wouldn't be a big deal, if not for the fact that every other Halo has been rated "M for Mature" (aside from Halo Wars and those Spartan twin-stick shooter games). Halo 5's potentially objectionable content includes blood, mild language, and violence, according to the ESRB, not to mention insults like 'Your father was a filthy colo and your mother was a hole in the wall!"

From everything we've seen so far, I wouldn't expect Halo 5's gore and interspecies taunting to be much more kid-friendly than that of Halo 1, 2, 3, 4, ODST, and Reach. Shifting standards at the ESRB probably had more to do with the change in rating than any kind of effort to "clean up" Halo 5 from Microsoft and 343 Studios; much like how filmmakers get away with more vulgar stuff in PG-13 movies today than when the MPAA first introduced that rating in 1984.

Halo: The Master Chief Collection: This is a compilation of four Halo games in which players assume the role of Master Chief, a genetically-enhanced soldier from the 26th century. From a first-person perspective, players use pistols, machine guns, grenade launchers, and futuristic weapons to kill humans and fantastical enemies in frenetic combat. Battles are highlighted by screams of pain, realistic gunfire, and large blood-splatter effects. Players can also use stealth moves (i.e., stabbing attacks or throat slashes) to kill characters; one scene depicts human characters crying out as their bodies disintegrate, exposing muscle and bone. Some aliens break part into pieces when hit, and soldiers' corpses are sometimes depicted amid large pools/streaks of blood.

Halo 5: This is a first-person shooter in which players assume the role of a super soldier (Locke) searching for a missing character. Players use pistols, machine guns, grenade launchers, and futuristic weapons to kill alien and human enemies in frenetic combat. Battles are highlighted by realistic gunfire, explosions, and occasional blood-splatter effects. Characters can also use “assassinations” to kill characters by snapping their necks, or by stabbing them with bladed weapons. The word “a*s” appears in the dialogue, as well as occasional taunts/insults (e.g., “I have copulated...with your genetic progenitors!”; 'Your father was a filthy colo and your mother was a hole in the wall!').