What are some games with great ambient sounds? For example the sound of leaves rustling in the wind, winds howling across frozen plains, a creaking wooden structure, machinery/engines in a spaceship etc.

When it comes to immersion, such kinds of ambience can be far more effective than music, for me at least. In some cases the two are even combined. For example the awesome Grizzly Hills zone in World of Warcraft. It's got one of the best zone soundtracks in the game : https://www.youtube.com/watch?v=mpyInx0ldfo and what is so cool about it is that the track is sort of a fight between an instrumental piece and the sound of a forest wind. The instruments dominate the first half of the track but then abruptly yield at around the 04:00 for the forest wind to introduce itself. From that point onward it becomes a kind of dance between the two, or a fight depending on how you want to look at it.

Any other awesome examples?

DICE games. First time I experienced it was with Hard Tapes on Bad Company 2. Absolutely divine soundworks.

Sanitarium
all of the Tomb Raiders

Secret of Evermore on the SNES.

Thief
Bioshock 1+2
Witcher 2 and esp. 3
Skyrim (the preivious games with mods)
Aces of the Deep - with sinking ships near - eerie.
Space Hulk - Vengeance of the Blood Angels (iirc)

Doom 3, (first) Dead Space, Stasis, SOMA, Outlast, Call of Cthulhu: Dark Corners of the Earth (once you get it working at all.) He asked about ambient sounds, not boob physics. xD

Sacrifice. Seriously .

That's actually a nice topic. The impact of (ambient) soundscapes on atmosphere and mood is (for me) pretty big.

One problem for me are games like Witcher 3, where both music and sounds are spectacular, but they tend to drown each other out. And then it would break my heart to turn off the great music to enjoy the great ambience, or vice versa. But I'm always tempted. I wish there was a "pause/play" music hotkey for situations where I just want to take in all the (ie. forest) sounds for a moment. Like a "hide HUD" hotkey for enjoying the scenery (and screenshots).

Can't forget about Unreal! and right from the start as well : https://www.youtube.com/watch?v=m4enxe0bpB8

Red Dead Redemption. You'll really feel you're in the Wild West.

Heretic 2 had ambience aplenty in the first few levels of the game, a town stricken by a mysterious disease. Generally not much sound apart from wind whooshing across the mostly empty streets, occasionally hearing the crying of a likely ill baby. Used to make me feel really uneasy...and then the ambience is ruined by the cheese of running into enemies who spout stuff like "I get his liver".

No clue if the game had great ambiance past that. Only made it as far as the swamps outside the city.

Also nomination for could've been good ambiance: Witcher 1. It did good work with ambiance right until a little too oft looped sound like a kid going "Blargh" at something he/she doesn't like which just sounded so artificial it broke the mood.

Good joke, but come on, there is some very nice ambiance in those; Area 51, the water dripping at the beginning of #4, waterfalls, any and all the jungle areas. I don't know, maybe I'm just easily amused. :P

Nah, you may be right though. I haven't played TR that much to remember. One TR I only played hardcore was Chronicles, and that game was so bad.

Listen to Ys: Origin - Water Prison