Nicest natural sounds

Walking in freshly lain snow

Heavy wind and rain at night battering against your window when you're in your bed

The tide coming in at the beach on holiday

New born lambs bleating on a spring morn

The echoing sound of a woodpecker drumming on a tree in the distance in a wood in the early morning
Hot summer's afternoon, the sound of turtle doves softly cooing
Kingfisher letting you know it is just about to fly by you by its high pitched call on the wing (great way to prepare for seeing these birds).

The hum of the mixer on the building site.