Have yet to see many of the performances mentioned previously but would definitely agree with the performances put forth in the Bicycle Thief and 400 Blows.  I would also give kudos to the job the star of Come and See did; great movie.  I am looking forward to seeing Kolya Burlaev's My Name is Ivan when it arrives in the mail in a few days as I have always heard what a great one it is.  But I have to concede that my all time favorite performance by a child actor has to be Brandon De Wilde in Shane.  The little guy never fails to bring tears to my eyes at the end of that film, and I don't care what anyone says, he deserved that Oscar nomination for Best Supporting Actor.