I'm sure most if not all of you are familiar with this week's favourite brick; the 1x1 'headlight' brick' is popular with builders thanks to its unique capabilities.
Beyond the regular uses of it in Studs Not On Top techniques where they are used to position pieces sideways, the pieces have many others uses because of their interactions with each other and other pieces.
Firstly, the headlights bricks can connect together to form an interesting square. This is because of the indent, and allows for the gaps to be filled in and an interesting shape created. It has been used by Dita Svelte to create a wall pattern: https://www.flickr.com/photos/24166730@N07/4498693420/
The next use is in obtaining a 'quarter plate', where 1x1 plates are attached to the headlights bricks to create the most gradual slope possible. This relies on the indent in the headlight brick, which is actually has a thickness of half a plate. When they are also attached to jumper plates, the quarter plate slope can be created. This has many applications such as roofs using 1x1 'cheese' slopes, like the one pictured.
Here is the piece on BrickLink: https://www.bricklink.com/v2/catalog/catalogitem.page?id=776#T=S&O={"iconly":0}