A variation of the ginormous mine holes we can dig on appropriate spots. For storage purposes.
Basicly, a modestly sized hole you can dig into the ground using either your hands, or a shovel, maybe with a few branches as pit-props.
This hole will have room for one liftable item. Such as a container, or even a corpse. The hole will fill itself up once "loaded".
So it dual purposes as a grave or a secret stash. (Or not so secret since the soil graphics will probably look disturbed.)
Basicly: A less useful, cheaper leanto which probably shouldn't decay. (Unless your recently deceased should spring from the soil like bony missiles.*)
*Upon writing, I suddenly remember that used to be a bug in a earlier version of Dwarf Fortress
I submit this idea for review by the forum horde.