Cfrock
Keep it strong
Resident Evil: Revelations. Perfect reason to own a 3DS.
Pretty much this. Revelations is astonishingly good and if you have a 3DS you would be making a mistake not getting it.
In addition, Mario Kart 7 is arguably the pinnacle of the series. I would highly recommend it.
You could always boost your library with some DS games that you can probably find cheap these days. The Professor Layton series is wonderful and I would advise looking into them if you like puzzles. In a similar vein are the Ace Attorney games. I freakin' love Ace Attorney and if you like funny, charming and clever games, you hit the bullseye with Ace Attorney.
Other than that, why not take a look at the eShop? Pullblox (Pushmo depending on where you are) is generally regarded as excellent, though I haven't played it myself. The Virtual Console also has many classics from the past too.