LED torches & batteries
Always light at your fingertips: keyring torches
The main feature of key ring torches is that they are small. They literally must be possible to be clipped onto a set of keys. But that doesn't mean those lights should not be functional. These are not lights to light up a forest, but shining light on your lock or quickly find a lost object under the sofa should not be a problem.
Key ring torches usually operate on an AAA battery or a lithium button cell. Because of the low energy use of the LED lamps they last quite a long time. It is obvious that these types of lights are more intended for the 'you never know' situations than for intensive use.