I have a DSi and a 3ds. I'm dating myself but I bought the 3ds with my internship money and later got a new 3ds with money from my first full-time job.
I don't know if it's my favourite but Pokemon X certainly has the most hours sunk into hatching eggs and chasing shinies
There were a variety of eshop games that really utilized the 3d effect well. Pushmo comes to mind but I'm sure there are others.
Nothing besides being generally baffled at why the power of 3d in the palm of your hand was being ridiculed by the gaming community. I now know it's probably 3d fatigue from all the 3d movies/TVs/etc around that time.
I dug my 3ds back out with the eshop shutdown and have been playing FFTA2 lately.
I like 3D. I don't know why it gets so much flak. True, the whole industry jumped onto it without figuring out the details and just wanting to sell sell sell... Which didn't work. But the idea isn't bad.