I'm starting a list of sound effects I can still hear when the sounds effects are turned all the way down:
1. morning rooster (sounds nearby)
2. placing blocks (echo only)
3. destroying blocks (echo only)
4. distant cackling (sounds nearby. I last heard the echo version with the biomes update)
5. Underwater bubbling (sounds nearby)
6. Bird chirping (echo only.. right-channel only) ( http://www.megafileupload.com/b54s/bird_echo.ogg )
7. occasionally i hear rock falling in water if i mine nearby, not always.. maybe its material specific.
8. using pick axe on dirt. I hear both the impact and the stones rolling down too.