I think you're thinking of MadWorld, which was developed by Platinum and published by SEGA. The shooting/sword game was Red Steel (and its sequel), which were published by Ubisoft.

However, Nintendo do have some M-rated IPs, and generally they're quite good in that they don't use graphic violence or shock value as a crutch (I'm looking at you, GTA). Here in Australia, most of the Fire Emblem, Xenoblade, Zelda and Metroid titles are M-rated, as was Disaster: Day of Crisis. The Project Zero games (Fatal Frame in the US) are MA here. There's also Bayonetta, which is looking more and more likely to just become a Nintendo thing, and they're MA over here.

I'd be quite happy for Nintendo to make more games in the caliber of those kind of series, though, since almost all of them are pretty excellent.

Also want to address this, since I hate that people have this misconception that anything under a million sales is bad.

Nintendo themselves said that they don't spend as much on marketing if they think a game is likely to find its audience anyway (because a lot of Nintendo fans and gamers in general tend to keep up with new releases). I believe the example they used when talking about this was Xenoblade. That lack of marketing spend also means their games don't need to sell anywhere near as much to be profitable; the companies who usually want to sell a bajillion copies of their games are the bigger third-parties (especially Western ones) who blow millions of dollars on global campaigns. Plus, Nintendo don't have to worry about licensing fees when they're self-publishing. Most of this is also true of Sony and Microsoft, which is why those companies are more able to release niche games for their consoles even if they only sell, say, 250k or something like that.

The reason I've picked up Wii in the first place was to play Rogue Squadron, Resident Evil 0 and Remake of RE 1, Ethernal Darkness and to play fps games with motion controls. I didn't care about any of the big time Nintendo franchises and today I only care about Mario Kart, Metroid and Zelda. In other words - absolutely yes. Nintendo needs more T and M rated exclusive games.

It also could mean they don't want to invest heavily in a game that could flop or not do as well or won't sell much beyond the game's fans. Regardless they are holding back on supporting their games in a sense. 

They should make good games.

The industry demands it and if they don't at least get Retro or something to be their "Rare" and do something like this, they're going to be in a world of hurt.

What is the point of showing the industry they develop games that are strictly for adults? The industry doesn't give a damn.

The majority of mature people don't play M-rated games, those games primarily target teenagers.

1998 called. They want their "should Nintendo make a mature IP" conversation back.

Nintendo should hold on to this thing that keeps them Nintendo. Their games are not exclusionary. They are for everyone. Having a USP in this world is so important, and in a games market that is absolutely filled with M-rated targets there is totally room for Nintendo. That's not to say it can't associate with and support M-rated titles as it has done in the past, most recently with the likes of Bayonetta 2, but the core of Nintendo should always remain family friendly and that is something I'm quite passionate about.

Nintendo is better served creating IPs like Splatoon, where it takes a genre typically reserved for M-rated games and makes it something that anyone can play.

Not really. They're supporting their games in a way that makes sense financially. Something like Wonderful 101 probably wouldn't sell substantially better with a massive marketing budget, it would just mean the game would lose money for Nintendo. This is why Ubisoft/EA/Activision mostly deal in gritty open-world games or shooters or sports games or movie tie-ins or other "safe" titles, because they're the ones where marketing might encourage Joe Average to buy the game.

If Nintendo's approach were to only make the kind of games that can sustain a massive marketing budget, games like W101 or Bayonetta 2 probably wouldn't exist.