The Grave Bandits (2012)

Armed with a slingshot.

Romy and Peewee are teenage orphans in the Philippines with an unusual job; they loot the cemeteries and steal precious belongings left for the dead. The townspeople are fed up with their disrespect for the dead that a hefty reward awaits for their capture. Desperate to flee the town, the sail to a desolated island only to encounter a greater foe - THE UNDEAD, victims of contagious alien virus that were unleashed from an ancient meteorite discovered by the obsessed American Scientist named William Seabrook. Trapped on an island and left with nothing to defend themselves, the grave bandits must use their wits to battle the swarm of flesh eating ghouls!