Perennial Basil, it helps keep the bugs off other plants and can be used in food.
Nasturtiums, they have pretty flowers and both the leaves and flowers can be used in Salad etc.
Jasmine, smells fab and you can use the flowers to infuse tea and homemade lemonade ( don't use the leaves though )
Lavender, looks and smells great and they can be used in baking. Lavender biscuits are devine! Lavender in a quiche is also good.
Rose scented geraniums, they are pretty hardy. They look and smell great and the leaves are great in herbal tea, you could also place a few at the bottom of you cake tins to make your cakes fragrant.
Thyme, very pretty and great in many dishes.
Lemon verbena, smells and looks beautiful and the leaves can be added to rice, fish, chicken etc. to flavour (just remove after cooking.
Rocket (arugula), great in salads and the flowers can be used as garnish.
I've got to many too mention, at my previous house I turned our entire yard into an edible garden for my kids.
"I used to jog but the ice cubes kept falling out of my glass."
"I hear voices and they don't like you "