I love Big. The scene with the giant piano inspired me to learn how to play. In all honesty, I can still only play that song and the Eastenders theme! Forrest Gump gets me everytime. I think Splash and Philadelphia are classics. The Green Mile has the perfect mix of humour, drama and weepy moments.
He is a brilliant actor, but I didn't like Castaway. I only watched it for the Wilson bit. I do have to acknowledge that it must have been a difficult role for him.