I actually make and sell cupcakes, and I definitely think it's the cream cheese icing. So much tastier than any sort of buttercream.
There's a reason red velvet is such a popular flavour when the cake is really just a rather plain and mild chocolate cake.
On that note, my favourite cupcake flavours are always the fruitier ones. I love carrot cake (I add a bit of pineapple) and I also love flourless orange cake. I just find them a bit lighter and more refreshing.
Such a hard choice! I don't have muffins very often because the are so calorific, but I think the traditional blueberry is my favourite. I am also partial to banana muffins. I think carrot cake is one of my favourite types of cake, but I've never had it as a cupcake, only as a loaf cake. Carrot cake does work exceptionally well with cream cheese icing.
There is a new cupcake store that has opened recently in a nearby shopping mall and they have gourmet cupcakes of every possible flavour. I can't get enough of Apple Crumble with Caramel. It's a little costly, but worth every cent.
I have to treat muffins and cupcakes as two very separate types of food, if I didn't then I would be eating chocolate cupcakes for breakfast all the time ;) Chocolate is easily my favourite cupcake, but it's the icing that makes the cake. I usually do a cream cheese icing or a caramel icing.
With muffins, hands down lemon poppy seed muffins are my favourite. I also love blueberry or even better blueberry lemon poppy seed! I also love raspberry white chocolate, but I tend to treat this more like a dessert.