One answer has mentioned “cwm”. It is true that w is a vowel this word (as you can tell from its pronunciation — “coom”). But there is a problem here — this word, and others in which w is used in exactly the same way are not English words! (which is what I assume you want), but Welsh.

In English w can be (or more exactly “mark”) a vowel, but NEVER all by itself. It needs to be the second part of a two vowel-combination (called a “diphthong”) – aw, ew, ow. In these cases it ‘behaves like a u’ (which is not surprising since “u” and “double u” ARE related!)

Here are some examples of this use of w, and with it the equivalent uses of u. (Note that, most often, the w is used at the END of a word, the u in the midst of it.)

paw, caw / pause, cause

few, slew / feud, sleuth

bow, how / bout, house

By the way, BOTH w and y are consonants ONLY at the beginning of syllables… anywhere else in a syllable they function as vowels.