I know LabelKing and another have already mentioned it, but I think Royal Tenenbaums (and really probably all Wes Anderson movies) deserves a bit more attention.
Hackman's suit is just the definition of awesome. Grey flannel pin stripe with a pink shirt and the perfect repp tie. He just wears the hell out of that suit.
Eli Cash has that unique leather jacket and that Stetson open road hat.
The fact that Chaz and his two sons wore matching black Adidas track suits to their father's/grandfather's funeral is just great.
Hell, even the house servant, Pagoda, is dressed better that I am in most scenes.
Finally, there's Danny Glover. He's got that great bright blue coat and matches it spot on with that blue gingham shirt.