What's the most "mature" Nintendo-developed game?

[GooseGaws]

@HappySqurriel:

I hate to continue to argue with you, but I have the Perfect Dark box sitting on the shelf right next to me and it clearly states "Published by Rare". If you look at the enlarged version of the box art in the Wikipedia entry, you can see it. Diddy Kong Racing and Jet Force Gemini were also published by Rare, though of course were not rated M.

@Danny355:

I'm not necessarily saying that it's more mature than the Zelda or Metroid series, just that the juxtaposition of the character design to the nature of the plot makes the mature themes stand out. As for "measuring" the maturity of a game's themes, it was just a question that I wanted to hear some opinions on. You don't hear about thousands of mushroom retainers meeting untimely ends at the hands of a vicious squad of mercenaries in the Mario games; as Nintendo traditionally has a more "family-friendly" image than many other companies, I was curious to know which of their self-developed titles had the most impact in this area in each player's mind, and whether the developers seem to be moving toward or away from those types of themes.

That's a hell of a long sentence.