I hate turning on lights at night just to go to the bathroom. When I do it hurts my eyes, wakes up the babies, and I lose my night sight once the light is out and stub my toe. If I just walk in the dark I can see fine until I need to aim for something like the toilet. Here is an easy gravity switched LED that sticks to the lid and doesn't put out too much light but just enough for that 2-am run.

Need to salvage an 3V LED from a happy meal toy or something.
2 plastic soda bottle tops.
A 3V button cell battery, CR2032
A penny
A paper clip
Some double-sided foam tape.

And some solder.

Step 1: Cut Tops of Soda Bottles

Cut the caps of two bottles, make one slice very thin, the other about half way.

Step 2: Solder the Setup

Solder the LED cathode ("-" side of LED) to the penny.
Then bend the anode sideways and solder on a little .25" piece of paper clip.

Step 3: Assemble and Glue Cap

Melt or drill a hole the size of the LED in the thicker bottle cap. (Aim it diagonally towards the bowl, not straight down like in my video and pictures.)

Mount the penny rig into the cap.

Then place the battery into the cap "-" side down; tilt it around and make adjustments based on how the battery contacts things. When you tilt it toward the LED, the battery should slid and make the "+" connection on the paper clip.

Take the thin cap slice and super glue it onto the base. You may need to file the cap cuts to make the pieces fit together better.

Tape it to the toilet lid and wait for the night.