The Goonies

The Goonies (1985) is a classic comedy about a group of kids (the Goonies) whose families are losing their homes for a rich entrepreneur to build a golf course. This underdog story is written by Spielberg. The kids, or "The Goonies", are a close knit and vibrant group, and they refuse to be forced to move from their lives peacefully. The main character, Mikey, is a cool, composed, and motivated young kid who is definitely the leader of the group and is the one who convinces all the kids to search for "Ol' One Eyed Willy"'s treasure.
Usually, people in an exploited situation like these families are powerless, just as this group is before they find the treasure. But this is a happy ending in that the weak and powerless group gains power with the jewels and treasures that they find by their hard fought journey to the abandoned pirate ship, with a little help from Lotney "Sloth" Fratelli.
The Fratellis are the bad robbers who the kids cross paths with by venturing into their house to get to the treasure. They chase the "Goonies" frantically to gain all the treasure they can for themselves. Mrs. Fratelli is definitely an ethical egoist, in that she uses all her sons to her own advantage. She even tries to hoax Sloth into siding with her during the fight for the treasure, lying to him and telling him how much she loves him.
In the end, the good guys come out on top and the jewels save the day for the Goonies. It makes for good film to see a David vs. Goliath battle won by the underdog, and this film certainly would fall into the category of an underdog story. For anyone who hasn't seen it, The Goonies is a must see.