Sometimes I put essential oils in a burner (I like peppermint oil, or a blend of grapefruit and ylang ylang), or use soy wax melts. The cheaper versions of scented oils and melts tend to give me headaches, I suppose due to whatever additives are in them.
I don't use air freshener or scents as I don't like the chemical aspect to them. However, I do burn Flametree Soy Candles with the most gorgeous perfume - "Black Raspberry". The smell is absolutely gorgeous and goes through the whole house. Just love them.
I use scented candles and air freshener in the loo. I love apple and cinnamon, spiced pumpkin and cherry scent, but cannot stand lavender, lily of the valley, rose or other fragrances that have been around for centuries. Love Yankee Candle.