The most famous variant is probably the one we already know from the can: just
tomato sauce and minced meat. Similar, at least in simplicity, are probably the ravioli Neapolitana. Here, ricotta, parmesan, egg and parsley are mixed into a mass, which you then fill into the pasta cushion.
A little more elaborate, yet with meat, are probably the
ravioli alla Genovese. Here, veal and pork are mixed with calf's brain and sweetbreads. To this are added egg, Parmesan cheese and bread crumbs. The typical Genovese green color comes from the addition of chard.
For the fish lovers there is of course also a ravioli variant. Here, in addition to the fish, spinach and egg are also added. To top it off, a touch of nutmeg is added. Sometimes you can also find processed seafood or even
crab.
But enough about meat and fish. The most famous vegetarian variants are probably the spinach ravioli, which obviously uses spinach. Here, ricotta is added to the spinach and, how could it be otherwise, also egg and Parmesan. Also, here nutmeg rounds the pleasure. In addition, there is the fasting version of ravioli: Ravioli di magro. Here only vegetables are used for the filling.
In addition to the filling, you can of course also vary the sauces. There are no limits to the imagination.