Latin does not have any monosyllabic words that end in a short vowel when pronounced in isolation. This is my formulation of a fact given by Diana Apoussidou and Paul Boersma in "The Learnability of Latin Stress", p. 115.
Monosyllabic words in Latin may scan as light syllables when followed by another word in certain contexts.
The most commonly encountered example is words ending in V̆C (such as in, ad, sed), which regularly scan as light syllables before vowel-initial words. In this context, the word-final consonant was apparently resyllabified into the onset of the first syllable of the next word. This resyllabification clearly occurred in poetry, and is believed to have also occurred in the ordinary spoken language, at least within a phonological phrase. Resyllabification of consonants before vowel-initial words also affected the weight of final syllables in words of more than one syllable.
Less frequently, you may encounter a monosyllabic word that in isolation ends with a long vowel scanned as a light syllable before another vowel. For example, you can find ŏ or quĭ scanned as short syllables before a vowel. This phenomenon seems to have a few names that aren't entirely synonymous: the term that I am familiar with is "correption". Correption of word-final long vowels seems to be described as a Greek-based practice in general, but for monosyllables it may have been normal in Latin:
Correption or "prosodic hiatus" of monosyllables is a special case, not confined to Graecizing contexts. It probably reflects actual *pronunciation. It is regular in drama, e.g. Plaut. Merc. 744 nam qui amat, quod amat si habet, id habet pro cibo. It occurs occasionally in Lucretius, Catullus, Virgil, and Horace's Satires. The non-elision of monosyllables ending in -m occurs with a similar distribution and should probably be counted in this category [...]
("hiatus", The Oxford Classical Dictionary, edited by Simon Hornblower, Antony Spawforth, and Esther Eidinow. This entry cites the following references: "M Leumann, J. B. Hoffmann, and A Szantyr, Lateinische Grammatik (1977), 1. 122-3; H Drexler, Einführung in die römische Metrik (1967); W. Lindsay, Early Latin Verse (1922), ch. 3; D. S. Raven, Latin Metre (1965)"; the contributor is given as Jonathan G. F. Powell.)
Elision of the long vowel (resulting in a reduction in the number of syllables) is an alternative possibility even for monosyllables, though. You can see more examples and discussion of conditioning factors for elision vs. correption in the article "Elision and prosodic hiatus between monosyllabic words in Plautus and Terence", by Kanehiro Nishimura (2016).
There are monosyllabic enclitics (not independent words) that (usually) end in a short vowel and scan light when followed by a consonant-initial word: -que, -ne, -ve.
Some words have phonologically clitic contracted forms that are non-syllabic: for example, est has the contracted form 'st, which is phonologically dependent on the previous word. (For more details on the contraction of forms of esse, see Terence and the Verb 'to Be' in Latin, by Giuseppe Pezzini, 2015.)