I love scented pelargoniums. As well as being easy to grow indoors or outside, they have the dual bonus of having pretty flowers as well as scented foliage. My favourites are those with rose or citrus scents; the balsam and mint ones are a bit too niffy for me.
Top row, left to right: Peter's Luck and Candy Dancer. Bottom row, left to right: Attar of Roses and Copthorne.
This is what they look like in situ. I can't really call this a balcony; it's a narrow strip of concrete outside my kitchen door - four floors up the fire escape and overlooking the car park.