Atmosphere

Red Dead Redemption has many items in the atmosphere.

Tumbleweed
Tumbleweeds are dried up plants that are usually rolling around throughout towns and in the wilderness. If you shoot one, it will break into pieces.

Cactus
Cactus are plants in Red Dead Redemption. If rammed with a Stagecoach, it will fall down.

Insects
Insects can be found around Red Dead Redemption. They include Ants, Beetles, and Butterflies. You cannot interact with them at all.

Rocks
Rocks are found everywhere in Red Dead Redemption. They are just for looks, they don't serve any purpose ingame.