My favourite sets are alpine, modern (ESPECIALLY when customised using gems) and polka dot. I have three rooms in my mayor's house that have one of those furniture sets.
The back room has the alpine set, customised with beige wood and the leaf pattern. Sadly, the alpine rug and wallpaper don't match it, so I used the green wall and neutral floor instead.
The second floor has the polka dot set. It used to be pink with custom designs because pink was my favourite colour when I made them like that. Now I have brown and blue furniture, with the blue wall and a custom designed carpet to match the furniture.
The room on the right has the modern set, customised with rubies and the bubblegum shirt. I think it looks so pretty! But I'm sure that it would look even better if it was customised with sapphires (because blue is my favourite colour).
Not sure if it counts as a set, because there isn't stuff like chairs or beds in it, but I also like the Nintendo items.
The Alpine and Rococo would have to be my favorites, the are just so pretty to me. Especially when you can customize them a little bit! I think that other sets that I like / often use would be Cabin, Pav?, Spooky and any other set that you can add a custom design too really, lol!
I love the mushroom set...and a lot of the bug items too.I got the caterpillar sofa a month after I started playing I was so excited to see it in my room.and it is still on display
Rococo it's so elegant I also like the Gorgeous set it looks fab in my Mayor's home I just use anything outrageously beautiful to make some sort of glorious casino mansion in my town lol xD definitely works with the theme I have going : P