I liked Snowpoint. The fact that it was out away from the rest of the world and the snow make it my favorite.
Canalave City. The history behind the library as well as the stories you were able to read was pretty cool. Jubilife was also my favorite, just for the relaxing theme.
Ardent user of anything Rock, Steel, Ground, or Fire3DS FC: 4296-3229-5439Credit to Mochi10 for the userbar/Sworn Metalhead for the awesome banner
Hmmm... Floaroma Town, Canalave City and Jubilife City are my favorites <.> Mostly because of the flowers, being able to go to Iron Island, and the GTS respectively.
Jubilife and Eterna. I just love the music.
Snowpoint or Floaroma. Both of their music is beautiful, but the thing i like most about those is that their calm, full of nature, and in solitude from the rest of Sinnoh. pure beauty. ;P
I like all of Sinnoh, but for the sake of time I'll say Veilstone, as it's one of my favorites: the Department store, the gym leader uses Lucario, and it's right next to the rainy area. What's not to like?
Thanks to Brutaka for the awesome banner!