Below is a list of all the ●SNAKE● ammo you can find during the game. The ●SNAKE● itself will be picked up when opening any of these chests.
Start Point?. Head to the far right of the map. It can be seen free to take on the platform.
Mimiga Village. Head directly to the right after exiting the First Cave. Climb onto the block on the chain on the left, and jump to the right. Your head will just barely miss the ceiling, and you'll be able to reach this chest with ease.
Pipeworks E. Climb up to the second set of pipes, and enter the one on the right. Hold to the right as you exit the other end, then climb up to reach this chest.
Grasstown. After you reach the auxiliary terminal at the top of the map, return to the Generator Room and head to the right. Take care in choosing which breakable blocks to break, and you can climb up to reach this chest.
Abandoned Facility. After defeating the boss of the area, head to the right to find it free of charge.
Outer Wall. Climb to the very top. Near the door to the Observatory, climb underneath the floor, and continue to the right to find this chest.
Devil's Garden. After reaching the final area, head all the way to the right to find this chest hanging above the final door.