A light plunger.
It sort of sounds like something from a sci-fi novel, doesn't it? (Like: "The Hubions are gaining on us, activate the light plunger!") In fact, it's a new product just launched on Kickstarter that looks like it combines the concept of a French coffee press with a table lamp and lets users plunge the light to turn it on or off.
And, while we certainly think "light plunger" would have been a good name for the device, it's actually called the DiMO lamp (although we're not entirely sure why.) And the makers say that it drew its inspiration from a syringe instead of a French press.
The concept is relatively simple. DiMO consists of a plastic tube contained between two discs of beech wood. Extending down from the center of the top disc is a plunger. As the plunger is pressed down, the light compresses until eventually it turns off, as the plunger reaches the bottom. Reversing the process turns the light back on and fills the plastic tube with light as it is raised. The plunger is designed in such a way that no light leaks past it, so the effect really is like playing with light as though it were a liquid.

The plunging action doesn't change the intensity of the LEDs embedded in the bottom disc, but it does allow you to control the height of light, which would control the way it beams out onto your table or desk.
There are two styles available: One has a plunger that simply slides up and down (the "Classic") and the other twists like a corkscrew (the "DiMO Plus"). Handles are customizable in either a simple lacquer or three other color options – red, white or yellow.
Right now you can put in a pledge for a lamp for the early bird price of £47 (about US$62). When those are gone, that climbs to £55, which is still a discount off the predicted retail price of £75. If all goes well, DiMOs are expected to ship in February 2017. That's quite a ways away, and crowdfunding campaigns rarely do go according to plan, so be prepared to wait for your light plunger. Just try to avoid the Hubions till then.
Sources: DiMO, Kickstarter