In the comics, from the 1960s to the 1980s, he was always immaculately clean-shaven.
In the 1980s, Roger McKenzie and Frank Miller took the character in a darker direction, and started emphasizing his working-class roots. With the film noir style, he occasionally had a five o’clock shadow.
When Rex Smith played him in 1989’s The Trial of the Incredible Hulk, he was clean-shaven.
I have only seen parts of the 2003 Ben Affleck film, but he was usually clean shaven.
Today, Miami Vice-style stubble is fashionable.