Ruler Tool:
Allows you to quickly measure the distance between two points. The points can be placed in an exact manner using either snapping or just moving them in the scene.

Angle Tool:
Measures the angle between three points in degrees. Points can be snapped.

Volume Tool:
Quickly calculate the volume of a room, plane or sphere. Points can be snapped to vertices or grid.

GameObject Tool:
Missing actions from the Inspector, such as Deselect, Reset Position/Rotation/Scale individually, quickly remove or move components up/down, a snappable rotate towards point-option for exact rotations without having to rely on numbers, and a quick button for renaming child objects.

The tool never creates objects in the scene, and never takes up space in the actual game once in play mode and thus doesn't use any valuable resources in-game. The user can also pick the color and the amount of decimals the tool displays.