On topic but...
A couple of those Camorra guys (and the girl) from Series 2, as well as Furio in later series.
Little Allie Boy Barese (there is that small clip of him meeting Tony later, and he looks like he'd aged since his cousin went away)
And yeah Gigi Cestone (incidentally, John Fiore does a great job as Al Nazolli in Brotherhood; a totally different kind of mobster but; instead of the stoic, steadfast and reliable capo Gigi, Nazolli, a boss, is kind of arrogant, cocky and, well, in love with himself a bit)
Corky Caporale, Chrissies "associate",

Generally though, I liked how characters that in earlier episodes were more or less background came to the fore in later ones, and how guys were always unexepectedly always either out or in, some stars rising and others burning out.