Halo 5: Guardians is now the first core game in the series to be playable by teens as it was granted a T for Teens rating by the ESRB.
"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!')."
Playing a few minutes of Halo multiplayer would make it very hard to believe, but all previous Halo titles have been rated M for Mature.
P.S. In case you're wondering, the word "colo" in the ESRB rating summary is Spanish slang for ass.