I own a 3DS (Blue) and 11 3DS games at the moment:
1.) Legend of Zelda: Ocarina of Time 3D
This game is great; the only problem I have with it is that it is NOT a "pick-up-and-play game"..you really should devote chunks of time to it.
2.) Rayman 3DS
This one had mediocre reviews so I backed off at first. I went out on a limb and snagged one for $20 total including shipping via ebay. LOVE IT. I never had the chance to play the original version of Rayman 2 (which this is a port of) and the graphics/3D effect are really good. Highly reccomended.
3.) Rayman Raving Rabbids Travel Through Time
At first I loved this 2-D platformer but after about 5 levels it became super repetitive. Good for a few laughs as the Rabbids are quirky and kids adore it.
4.) Street Fighter 4 3D Edition
As stated many times on CAG and various sources this game is pretty awesome. One of the best 3DS launch games IMO. Excellent graphics, gameplay and replay value.
5.) Dead or Alive Dimensions
I loved this game just a little more than Street Fighter as I feel it requires more skill. Fun times, especially the tag battles.
6.) Resident Evil Mercenaries 3D
A game people are/were on the fence about. I love it but now that I've played a good 5-6 hours of it it didn't feel like $40 worth of a game to me. Graphics and gameplay are awesome, don't get me wrong, but shooting zombies with no core gameplay/story get a little old after awhile.
7.) Ridge Racer 3DS
A pretty decent racer, I'd snag a copy if you find one at the $20-$25 range if I were you.
8.) Tom Clancy's Ghost Recon Shadow Wars
My favorite 3DS game so far. I'm a huge fan of Final Fatasy Tactics and Front Mission 3 so that may be a huge factor.
9.) Tom Clancy's Splinter Cell 3D
I haven't out more than 12 minutes into it so far but it looks promising.
10.) Cartoon Network Punch Time Explosion
The fighting seems a little shallow...like the attacks don't feel impactfull enough. I've only put 30 mins into it, I'll need to explore a little further.
11.) Pilotwings Resort
Maybe Pilotwings isn't my thing, but this game is not doing it for me. Really boring. They should have packed this game with the system IMO so you have something to play out of the box, as it's just not worth spending more than $15 on.
I also picked up the extended life battery with charging base included (Nyko I believe). It's a good buy but for some reason my charging base has stopped working.
That and any clip-on armor will not fit while the battery is installed. Extends battery life by about 2-3 hours.