The things the soldiers carry are far too many to list here. It might work better to categorize the things the men carry. For instance, the men carry personal items from home (letters and pictures), items of personal necessity (toot brushes, pocket knives, Kool Aid, and desserts), items belonging to soldiers (machine guns, boots, helmets, flack jackets), items based on rank and expertise (Henry Dobbins was a large man so he carried a larger weapon and Rat Kiley was the medic so he carried morphine), items that varied based on their missions (machetes and bug juice), items based on superstition (a Bible, a sling shot, dope).
In addition to these, O'Brien observes they also carry themselves, ghosts, the land itself, emotional baggage, and - the heaviest burdens of all - the memories of the fear they experienced and the things they did.
The second link below takes you to an excellent critical source that analyzes the physical and mental burden the war has on the men.