Here you can find other Italian nouns that show some peculiarities.

Nouns ending in –ione and -udine are generally feminine, nouns ending in –ore are generally masculine:
la nazione - the nation
la televisione - the television
l’abitudine - the habit
il professore - the professor
l’autore - the author

Some nouns ending in –ore in the masculine can form the feminine either in –essa or in –rice:
Il dottore, la dottoressa - the doctor
Il professore, la professoressa - the professor
Il pittore, la pittrice - the painter
L’attore, l’attrice - the actor, the actress

Other nouns can form the feminine in –essa:
L’avvocato, l’avvocatessa* - the lawyer
Il principe, la principessa - the prince, the princess
Il conte, la contessa - the earl, the countess

* the form avvocata is also used as an alternative to avvocatessa.

Nouns ending in -cia and -gia maintain the i in the plural only if they are preceded by a vowel, otherwise they drop the i:
La camicia, le camicie - the blouse, the blouses
La ciliegia, le ciliegie - the cherry, the cherries
L’arancia, le arance - the orange, the oranges
La spiaggia, le spiagge - the beach, the beaches

Masculine nouns ending in -io, generally form their plural with only one -i
L’operaio, gli operai - the worker, the workers
Il fornaio, i fornai - the baker, the bakers