MAILMAN

Mailman is a Gameboy platformer where you play as the titular "Mailman," as he adventures out of a cave, collecting his lost mail on the way. 

In this game, you have a bag, which functions as a whip! use this bag to attack enemies, but avoid attacking the Lil' Rockies, as they mean no harm, and may help you in the future! 
The game also includes a variety of optional abilities, obtained in special locations.