The rustle of the wind in trees in the summer night.
The sound of summer silence. What is summer silence? It's the sound that you get when you're out walking on a dirt road somewhere in the summer and you're just far away enough from traffic for it not to be heard, there's really no one around and there's just this silence. Only it's not really silence, there's crickets and cicadas sounding and in the distance there may be a horse snorting. So basically the sound of that calm, combined with the steady thump of your shoes on the warm dirt road.
On the subject of silence I'd add the silence of a city in the early morning when it's empty. It's an entirely different being from the day. Just the sound of a city after midnight is completly different from the day.
The fissing sound of throwing more water on the sauna.
The sound of wind chimes near the sea.
The sound of dragging my hand against my beard stubble.
The deep roar and rumble of a V8 engine.
The exhited inhalation of a women when I've just found her sensitive spot. On a related note most all related sounds a woman makes during...pleasurable activities, but mostly the deeper, softer ones. Not one for shrill sounds.
Those are some I can think of. Kind of fun subject since I'm one of those guys that really likes to listen to things. Part of it is the fact that I hear everything, and focusing on a sound helps me concenctrate.