I so love everyone's responses and definitely kids laughing is a good one. I love the silly "woo-woo" howl my dog does when she is greeting me home. She doesn't bark hardly at all it is always this kind of wolf howl noise. I absolutely love the still quiet of the outside during a heavy snowfall. Everything is so muffled and peaceful and clean but you can hear a twig snap from a deer in the woods from a long ways off or the soft "whumff" noise when a buildup of snow falls from a bare tree branch. I always lift up thanks when I am outside at home during a snow. I am thankful for the serenity and beauty of the moment and very thankful I have a warm safe place to be.
Birds singing is a good one as well as a raptors cry. A cat purr or the purr-meow combo they often make when they have something good to tell you. Loons on a lake at dawn. A crackling campfire. Thunder in the distance.