Top three are:
3rd: Drive (It's a secret song that only plays when you make an invalid request.)
2nd: K.K. ?tude
1st: K.K. Flamenco
Good lord I love K.K. Flamenco! It's so catchy!
There are a good amount of tracks that I like. I've forgotten all of them, so I'll just list a few:
K.K. Bubblegum - I absolutely love this track! It's just so cheerful and innocent. It's on my Stereo most of the time in my Animal Crossing: New Leaf house.
Two Days Ago - Again. Another great track. It has an element of sadness to it, but I like those kind of songs. Loved it since I heard it on Wild World.
Forest Life - Very nostalgic song. It's got a memorable tune.
Only Me - Also a song with a hint of sadness in it. It's not too over the top, but it's still very nice. That's why I like this track.