While Shutshimi is obviously meant to be a party game, it's very fun for the solo gamer as well. Once you start learning what items do what, you'll be able to avoid the ones you dislike and grab the ones you dig. Shushimi is a nice surprise—I highly recommend it.
Like its predecessor, I got enveloped in Project X Zone 2 and kind of hate myself for it. But I enjoy the hell out of it, and if hearing Chris Redfield call Leon "Future Leon" with a straight face is wrong, I don't want to be right.
Typoman is a gorgeous game with a lot of half-baked ideas (and physics) and, frankly, deserves better. As it exists, the game is not worth recommending.
Chibi-Robo: Zip-Lash is a fun game. It's got some frustrating moments (stage select, vehicles) but the highs outweigh the lows, and I like the Amiibo functionality. Give it a shot, kids.
NOVA-111 scratches a very particular itch that I didn't realize needed scratching.
If you already have Shovel Knight, you can play this for free today. For people who haven't already bought Shovel Knight on whatever platform you own, what's wrong with you? It's one of the best games I've ever played, and this massive content pack doubles its scope. Acquire it for shovelry!
It's also worth noting that this is the second piece of software that's exclusive to the New 3DS, so if you're itching to get some use out of the thing, Binding of Isaac: Rebirth is your only other option after Xenoblade.
I highly recommend Xeodrifter no matter what system you get it on—and by getting it on one, you'll automatically have it on both. It's a win-win!
This is an incredible game, and one of my favorite on the 3DS. You should at least play the demo. If it hooks you, the full version is well worth your time.
Despite the game's AI issues, Never Alone is definitely worth playing—maybe with another person. It's a very short game and can be finished in two or three sessions. But it's the educational aspect that I appreciated most, and I imagine you will, too.
200cc performs shockingly well online, although I feel like I'm having more dropped games overall than I had prior to the 2nd DLC wave. I will say that racing online in 200cc makes me feel a little better about myself as I watch other human players go through the exact same struggles I am. This second DLC pack is great—better than the first—and I highly recommend it.
Trine: Enchanted Edition is a good game, well made and competent, but not necessarily for me. I can appreciate what it has accomplished, but its slow, methodical brand of puzzle platforming and the "meh" combat leave me wanting.
In the end, Rainbow Curse is a good game that provides plenty of content for both single players and a group of friends. I'm annoyed by the length of some stages, however, and it's a real shame that the player controlling Kirby cannot have the same viewing experience that the others players have. Thankfully, the core gameplay remains very enjoyable and I can still recommend it—but you should know what you're getting into.
UPDATE: I fixed the scaling issue. I just had to go into the Wii U Settings and shrink the bounding box a bit. Worked perfectly!
But the core gameplay—puzzle-solving with clones—is distinctly enjoyable. In a way, it reminded me of the Clank puzzles in Ratchet & Clank Future: A Crack in Time, but on a 2D plane. If that kind of puzzle-solving is up your ally, I'd give The Swapper a try.
If you liked the original Theathrhythm, this is more of the same with plenty of bonus content. It sucks me in every time I turn it on, to the point where my wife is actually pulling the headphones out of my ears to get my attention. It's a wonderful game. You should totally play it.
The Fall is a relatively short game, just a few hours long depending on how many puzzles stump you. The story is the most engaging thing, providing a unique take on the Three Laws of Robotics (although the laws themselves have been changed). There are really only three characters, but they're all well developed
[W]hatever version you have access to, I can't recommend Shovel Knight any higher.
[T]his is a wonderful game that I obviously can't stop playing, and I can't speak highly enough of. Endlessly charming and unusually engaging, Tomodachi Life is a fantastic diversion.
Swords & Soldiers isn't especially long, containing three campaigns with 10 missions apiece, but you can go into Skirmish mode for practice sessions and unlock some interesting mini-games. There's even an interesting two-player mode in which one player uses the GamePad and another play uses the TV and a Wii Remote, which is fantastic.