E for Exciting!
Although it's not set to release until 2015, ESRB has already given Nintendo and Intelligent Systems' new Codename: S.T.E.A.M a "T" (Teen) rating.
ESRB cites Blood, Fantasy Violence, and Mild Suggestive Themes as reasons, as well as noting that online gameplay "may expose players to unrated user-generated content." Here is a short, full rating summary for the game as it stands in its current stage of development:
"This is a role-playing game in which players battle aliens in an alternate version of Victorian England. Players command groups of characters through turn-based skirmishes and use steam-powered weapons (e.g., rifles, hammers, grenade launchers) to kill alien creatures. Combat is highlighted by explosions, cries of pain, and brief bursts of red blood. Some levels allow players to shoot from turrets or tanks in more frenetic combat. Female figures are occasionally depicted in revealing outfits (e.g., low-cut tops); one figure is depicted on a “victory” screen each time the player wins a skirmish."