Thrilling forum

John Huston's The Bible: in the beginning... (La bibbia) (1966), as Nimrod's builder. Only a short uncredited part, but this sequence about the tower of Babel was originally much longer than the short little sequence we see in the finished film, so Gianni's role was probably more significant than what we see here.

Fuga dal paradiso (1990) as Council member
Also credited even though this is an extremely small role where he's seen only on a monitor and has no dialogue

Remark :
here is the missing credit for Giovanni in I grandi camaleonti (1964) (Tv miniserie)
in fact it is episode 4 and not 3. role not given. (see page 4 - picture put by Nick)

The Appointment (1969) as Lawyer

In the rare sci-fi anthology TV series Ora zero e dintorni - episode 7: "Drugstore" (1980) as Tom

Sanguepazzo (2008) credited, as Doctor

The Pink Panther (1963) as Court clerk

It Takes a Thief (TV series), season 3, episode 9: "The King of Thieves" (1969) as Priest

Very tiny but credited role in Professione fantasma (TV series), episode 2: "Un'espressione inconfondibile" (1998) as Notary

Maciste nell'inferno di Gengis Khan (1964) as Captain of Vladimir's army