With basketball and baseball covered, I feel like it's gotta be football to round it off.
Remember the Titans is always good. There's Jerry Maguire if you want that sports management angle. Personally I've got a soft spot for The Replacements, and Any Given Sunday has that amazing Al Pacino scene. And then there's Waterboy if you want a big tonal shift.
Refrained from suggesting Rudy considering it's mostly just an ego puff piece commissioned by the guy himself. It's a fine enough underdog story "inspired" by real people, but knowing the backstory really diminished that movie in my eyes.