So many to choose from! I like his comedies and romcoms with Meg Ryan - 'Sleepless in Seattle' and 'You've Got Mail' - and also 'Big'. 'Saving Private Ryan' is one of the great war movies - very poignant and powerful. The opening sequence is already legendary for its realistic portrayal of war, but Hank's performance throughout is first rate - perhaps his finest of all - as a soldier who is war weary and mentally scarred, but still dedicated to his men and his cause.
But my favourite film is 'Apollo 13'. Such an authentic script, great realistic acting and great dialogue. Even though we know the outcome of the mission, the ending is moving.