If child performances count, which I suppose they do, Christian Bale in Empire of the Sun
I see from IMDb that he'd been in a couple of TV things and a film called Mio min Mio
(great title!) but for all intents and purposes, Empire of the Sun was where he arrived.
Originally Posted by Porkchopexpress
Eric Bana 'Chopper'
Good call, Mr Chop. Powerhouse performance.