Wikipedia tells me that Eternal Darkness: Sanity's Requiem was the first Nintendo-published game to get an M, and was even the first GameCube game to get an M at all, but yeah it was developed by Silicon Knights. Geist was the 2nd Nintendo-published game to get an M, but developed by n-Space. However, it says they worked very closely with Nintendo and had input from Miyamoto as well.
So Nintendo's dabbled with M-rated game development, but I don't think they've ever developed an entire M-rated game on their own. Luckily, the M stands for manly and has nothing to do with maturity. Brain Age is a million times more mature than anything else ever.
Favorite Companies: Nintendo, Blizzard, Valve.
Recent New Favorites: Grasshopper, Atlus. (R.I.P. Clover.)
Heroes/Homies: Shigeru Miyamoto, Gunpei Yokoi, Will Wright, Eric Chahi, Suda51, Brian Eno, David Bowie.
Haiku Group: Haiku Hell.
Nemeses: Snesboy, fkusumot.
GameDaily Article that Interviewed Me: Console Defense Forces.
