That is such a hard question. There are sooo many.
Old fashioned roses, Regal lilies, Viburnum carlesii, Mahonia, Sweet peas, Jasmine, Hyacinths, Philadelphus....I could go on and on...and then there are all the leaves of herbs that when crushed smell wonderful...oops must stick to the question!
I adore the smell of - sweet peas, honeysuckle, roses, lavender, philadelphus, narcissus and I have a rock rose that smells divine too.
Rosemary has a lovely strong smell if you touch it as you walk by.
Mmmmmm I love lavendar as well, I just bought several plants to put into my new garden. I also use lavendar in my cooking, make teas from, I just recently bought a lavendar exfoliating body scrub and.... well, lavendar is just great. It also attracts beneficial insects into the garden.