Not counting click languages, what is the oddest sounding language to speakers of English?

The weirdest sounds cross-linguistically would have to be those with a different airstream mechanism to the normal, pulmonic egressive mechanism.

The normal pulmonic egressive mechanism is simply making the sounds while breathing out of your lungs.

The lingual ingressive mechanism involves making sounds while sucking in air around your tongue. Those are, of course, clicks.

The two other mechanisms are:

• Glottalic ingressive: gulping down around your throat. Those are Implosive consonants. Found in Africa and Southeast Asia.
• Glottalic egressive: popping air out from around your throat. Those are Ejective consonants. Found in the Caucasus, the Americas, and some parts of Africa.