I'm rather partial to
Il Trovatore and
Rigoletto myself, though
La Traviata was the first of the Verdi operas I saw...
I assign Donizetti operas.
L'Elisir d'Amore and
Lucia di Lammermore are highly recommended.
Una Furtiva Lagrima is such a beautiful aria.
And Rossini operas too. They're wonderful - I can probably hum most of
The Barber of Seville from memory from listening to it so much. But don't ask me to sing - my voice isn't exactly operatic and probably belongs in Mordor.
Actually, I'll assign all of the Bel Canto composers. Bellini isn't performed nearly as much as deserved.