"Can't" in current common usage does not mean what it means. It most often refers to things we would not do because we do not like the consequences, but that we are *capable* of doing. It's an YUGE issue, because it allows people to rhetorically *escape* responsibility from things that they would *rather not* do, not that they are not *capable of doing* them but *choose* not to. Having said that...

For many of European background:
The "click" that is common in some African languages.
The "chkch" in Hebrew.
Some of the consonant combinations in Russian. "ny" "kv" and others.
Some of the sounds in Vietnamese.

Off the top of my head. I am sure there are more that are not occurring to me, or that I am not even aware of due to my own linguistic background. Anyway... ("Can't" hahaha!)

Saul