Roberto Benigni

No, his english isn't so good, but he can improvise well. Witness such in Down By Law. Ahhh...his other movies include Night On Earth (well, one fifth of it at least), Johnny Stecchino (Johnny Toothpick), and The Monster (Il Mostro). A few other things, Nicoletta Braschi is always the female lead in his movies (at least his Italian ones). His latest movie is Asterix and Obelix vs. Caesar, which hasn't found a theatrical distributor in the US yet, and probably will go to video sometime soon. His current project is a new adaptation of Pinocchio. The only other movies of his that have shown up in the states was Son of the Pink Panther, which MGM recently decided to salvage after a lot of people wanted to forget it, and Seeking Asylum, a 1979 Italian drama that shows very little of his insane comic side.

Other than those, the rest of his work hasn't really seen the light of day on American shores. Fellini's final movie The Voice of the Moon, The Little Devil (with Walter Matthau as a priest!), Nothing Left To Do But Cry (co-written by and co-starring the late Massimo Troisi from Il Postino), You Upset Me (his directorial debut and the first movie he made with Braschi), and Berlinguer ti voglio bene (his acting debut), among others, aren't even available on video or otherwise in the US. Maybe after he wins another Oscar...

Roberto Benigni is one of the best Italian comedians.
Describing Benigni is difficult; he started doing poetic improvisation in city squares. This is a tradition in Tuscany, the region of Italy were he was born.
Tuscanians in Italy have a reputation for being witty, sarcastic, sharp-tongued and difficult to bear. Benigni fits perfectly the description.
His mass media debut was in Italian state television RAI, back in the BW era. After an episode where Benigni called the Pope "Woytilaccio" (which means more or less "that bad ass dude, Woytila"), RAI vowed that they wound never transmit Benigni live again.

Roberto Benigni is a comic force of nature. Even the way his forehead wrinkles is funny.

When RAI, many years later, readmitted Benigni live it was in a show where he would be more or less controlled by Pippo Baudo. Baudo is a very conservative, predictable show host.
Benigni said "Pippo, I love you so much I want to swap pants with you". Now, Baudo is probably one foot taller than Benigni. But there was no talking the little man out of it. So they swapped pants. Live. On national TV, and at prime time.

Of the movies mentioned above, my favourite ones are certainly "Non ci resta che piangere" (Nothing left to do but crying) and "Il piccolo diavolo" (The Little Devil). In the second one, the contrast between the grumpy Walter Matthau and the far-out little devil that does not want to go back to hell is a source of endless amusement.