The Lock Lite. Turn your key into an LED flashlight by embedding it into this clever bulb and battery enclosure. You do need to be using a key which fits the particular shape of the device, but apart from that it should save many a weary hour hunting for your keyhole in the dark. £3.99.
Even if you’re not attempting in vain to unlock your door, the LockLite provides ample illumination for other tasks, emitting a light source that is visible up to a mile away. The batteries are replaceable and the bulb has a 100,000 hour life, so unless you’re unusually challenged at lock finding, it may well last you forever.