I guess we sould have specified what we meant by Italian - Reinhold Messner from up in mountains is Italian as was Primo Levy; their names tho’ are not ethnically so.
One of my classmates in graduate school had the last name of DeSantis. 100% Italian.
Nearly all words in standard Italian follow a C*V syllable structure - i.e. that nearly all syllables must end in a vowel. That’s where you get the stereotype of the Italian adding epenthetic -a’s to the end of English words that end in consonants (much as Spanish speakerrs, whose language forbids syllable-initial s+consonant clusters, will epenthesize an e- to the beginning of such words.)
So, by the analogous sound changes, a word that ends in a consonant in other Romance languages, such as francés/francès/français, in Italian you end up with francese.
Common names derived from Italian roots – e.g. names derived from common nouns or names that have been around long enough to have undergone the Italian sound change - thereby follow this vowel-final pattern.
“Italian” as a name for a language is ambiguous. The modern Italian language is the language of Tuscany, or more specifically, Florence. Italy as a nation has existed for such a short time that the regional “dialects” that originally were found all over the Romance-speaking world have not disappeared, and many parts of Italy still have quite vigorous populations of “dialect” speakers. How these dialects are categorized is not a simple matter; it’s silly to worry about whether a language spoken on the border of France is more like French or Italian, since it’s not really either of them.
My point, then, is that deciding what counts as “Italian” is difficult, even when you’re only considering speakers of Romance languages and not looking at all the speakers of Germanic languages. Any surname of Tuscan - that is, standard Italian - origin would end in a vowel, since in Tuscan all words end in vowels with the exception of recent imports and certain very short grammatical words (that can’t occur at the end of an utterance and thus can be analyzed as proclitics - that is, words that attach themselves to the beginning of other words.) No Tuscan name would end in a vowel. But then, a lot of Italy has or has had native speakers of languages very different from Tuscan. In those parts, without a doubt there are people with names left over from before Tuscan was predominant in the peninsula.
So if the name is of Tuscan - standard Italian - origin, then it will end in a vowel. If it’s not, it might not. Deciding whether a name originating from Sardinian, or Calabrese, or Veneto, or Ligurian, or Sicilian, or Milanese, or Neapolitan, counts as Italian is not a simple matter.
Admiral Canaris, head of the German military intelligence agency, who undermined Hitler and supported the bomb-in-the-bunker plot, was descended from Italians on his father’s side. So we have another s-ending Italian name.
While Tolliver is actually an Anglicization of an Italian surname (Talliaferro), it’s used frequently here in the US by Italian families.
Ceasar 
That’s Caesar!
Several posters have already said what I came here originally to say: Standard Italian ends words almost exclusively in vowels, mostly A, E, O, and I. The few cases where it doesn’t tend to be borrowed words. It may be worth noting that Standard Italian uses vowels to express plural.
Most, perhaps all, Italian last names that don’t end in a vowel will not be standard Italian. They may be from another language or dialect, or, in the case of Italian-Americans, they may be an attempt to make the name fit a more American mould.
I have heard that last names from the north of italy tend to end in ‘e’ or ‘i’ (that’s typically a plural word) and those from the south tend to be ‘o’ or ‘a’ (singular). My last name ends in an ‘o’ and comes from Sicily.
I believe Italy followed the pattern of the rest of Europe in that most people didn’t have fixed last names until relatively recently. The rich and powerful may have had last names (sort of), but the mass of people didn’t.
As for Caesar, he wasn’t Italian, he was Roman. (This may possibly explain some Italian names not ending in vowels, I don’t know).
Illona Staller, Italian porn star and Member of Parliament. I think she was born in Hungary, though.
I had a teacher once named deBenedittis.
I hate to point this out, the board being what it is, but Rick Santorum is the son of Italian immigrants.
Rick’s ancestors didn’t happen to be named dei Santi, did they?
As I understand it, that’s because standard Italian took its nouns from the Latin nominative case (-us, -i; -a, -ae, in Italian -o, -i; -a, -e) whereas other Romance languages such as Spanish, Portuguese, Catalan, and French took it from the accusative case (-o, -os; -am, -âs).
That’s the usual explanation. Tuscan also lacks the -s second person singular marker in verbs: Spn./Port./Cat. cantas, Fr. chantes, but Ital. canti (. I’ve read explanations based on purely phonetic principles, but I’m inclined to believe that analogy played a role: verb endings with consonants probably lost them because the entire phonological system was altered so that the lack of final consonants became systematic.
From the FAQ on that site:
My 4th grade Italian teacher, Signora Bassett. Though now that I think about it, that double T is a bit suss. Do you think it could have been changed?
Bassetto could easily have become Bassett upon immigration. A lot of immigrants had their names changed by officials at Ellis Island to more Anglo-sounding names. It happened to Italian names too, though not as much as to East European names. I always wondered why more Italian immigrants were allowed to keep their names.
The first name that came to mind when I saw the thread title is Giuseppe Sagarat. His name impressed me as really unusual for Italian because of that hard final stop -t.
The Italian names that end in softer sounds, like -n, -r, -s, don’t sound so anomalous in an Italian setting. The -s ending might be a Latinism in continued use, or it might be a plural form.
One reason so many Italian names end in the plural -i is because the family was treated as a plural entity. Lorenzo de’ Medici literally means ‘Lorenzo of the Medici (people)’, although the implied singular form *Medico isn’t actually used. When Catherine de’ Medici married the king of France, the French called her Cathérine de Médicis, making a double plural just so there was no mistake. (Not everyone in France would have been acquainted with Italian grammar.) The abbreviated form de’ is short for dei, which includes the masculine plural definite article -i as a plural noun marker. So I’m guessing some of those -s endings on Italian family names might have been added during periods of French and Spanish rule of Italy.
How’s’about Julius Caeser, Marcus Brutus, Lucious Crassus, Biggus Dickus…
My understanding is that the idea that many immigrants had their names changed at Ellis Island is a myth - the staff there included interpreters for dozens (maybe hundreds) of languages, and there was a lengthy interview with new immigrants. Further, reasonable proof of immigrants’ identity - papers of some sort - was required. So there would have been no difficulty with establishing their proper surnames, and as I’ve heard it most surnames were anglicized voluntarily. (Why Italians would seem not to have done so in many cases is a mystery, as Italians were not generally regarded favorably at those times.
I wonder if the name is Catalan, since it struck me as a very plausible Catalan word; then again, it may be from an Italian “dialect” with substantially different phonotactics from Standard Italian.
Except that plurals in Standard Italian are formed with vowels, and any surviving Romanism would be expected to undergo the same phonetic changes that the Tuscan language - itself of course a Romanism - underwent. I suspect that most of these anomalies either come from other, substantially different Italian languages, or else from migration within Europe.
I know Italian plurals are formed with vowels, my point was that French and Spanish plurals add -s, and Italy was under French and Spanish occupation for centuries. My guess was that these were native Italian names already ending in the plural -i, and the double plural -s was added because of French or Spanish influence, as happened with Cathérine de Médicis.
Do you happen to remember the bit from “The Sopranos” in which they talked about Italian names ending with a consonant being better people or something like that?