...perhaps Bobby Driscoll's is one.

From Wikipedia -
Robert Cletus "Bobby" Driscoll (March 3, 1937 March 30, 1968) was an American child actor known for a large body of cinema and TV performances from 1943 to 1960. He starred in some of The Walt Disney Company's most popular live-action pictures of that period, such as Song of the South (1946), So Dear to My Heart (1948), and Treasure Island (1950). He served as animation model and provided the voice for the title role in Peter Pan (1953). In 1950, he received an Academy Juvenile Award for outstanding performance in feature films.
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Driscoll was the first actor Walt Disney put under contract, to play the lead character in 1946's Song of the South, which introduced live action into the producer's films, in addition to extensive animated footage. The film turned Driscoll and his co-star Luana Patten into child stars, and they were discussed for a special Academy Award as the best child actors of the year, but in 1947 it was decided not to present any juvenile awards at all.
http://en.wikipedia.org/wiki/File:Oscar_march50.JPG
Bobby Driscoll receiving his Academy Award
from Donald O'Connor, March 23, 1950
Later, the child actor's life deteriorated...
When Driscoll left Chino in early 1962, he was unable to find acting work. Embittered by this, he said, "
I have found that memories are not very useful. I was carried on a silver platter ... and then dumped into the garbage."
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He left
The Factory in late 1967 or early 1968 and, penniless, disappeared into Manhattan's underground. On March 30, 1968, about three weeks after his 31st birthday, two boys playing in a deserted East Village tenement at 371 East 10th St. found his body. The medical examination determined that he had died from heart failure caused by an advanced hardening of the arteries[58] because of his longtime drug abuse. There was no identification on the body, and photos taken of it and shown around the neighborhood yielded no positive identification. When Driscoll's body went unclaimed, he was buried in an unmarked pauper's grave in New York City's Potter's Field on Hart Island.
When you wish upon a star, makes no difference who you are.
When you wish upon a star, your dreams come true.
Second star on the right, straight on 'til morning, my little friend...
Tom Russell has recently captured Driscoll's story in song: