Select Center Objects

Select Center Objects is used to quickly select all objects with geometry on the positive and negative sides or a chosen axis.

For instance, if you have a design in your scene, that consists of multiple objects, where some are at the center, perhaps positions along the Y or Z axis.
Other objects are then mirrors across the world X axis.
In such a case you can use the tool to very quickly only select the center objects - the ones that aren't mirrored across X.

Object Context Menu

Select Wire Objects

Select Wire Objects is used to quickly select all visible objets with a display_type set to WIRE.
Addons like Hardops or MESHmachine use wire objects to distinguish boolean operants from other objects.

Object Context Menu

Modes

ALT hide wire objects instead of selecting them
CTRL include empties as well

Select Hierarchy

shortcut Down in object mode" shortcut SHIFT + Down in object mode" to include the parents in the selection

Select Hierarchy is used to quickly select all children of the selected object.

What makes this different from Blender's native Select Grouped, is that it works on the entire object selection, not just the active object, and that it supports optionally unhiding hidden child objects.

Object Context Menu

Modes

SHIFT include parents as well

Using Select Hierarchy