The Ernest Borel flash and the Tourist everlight are two relatively unknown watches with a complication that is extremely rare. Most collectors have probably never heard of these watches or the complications, because they are so rare (and the complications are typically not in working condition).
The Tourist everlight and Ernest Borel Flash are both unique watches due to the usage of electric lighting bulbs.The watches can be lit up by pressing a button to the right of the case, similar to a chronograph button.

Ernest Borel was the first to file for a patent for an electrically lit watch, though the Tourist Everlight was commercially released before the the Ernest borel flash. Both watches are visually very similar and the complication also works more or less the same. The only major difference is that the tourist everlight has the light bulb on the dial, while the ernest borel flash has the bulb hidden in the movement.

As can be seen on this picture, the light is visible due to the dial markers not actually being markers, but rather holes cut in the dial. There is also a empty ring around the movement to allow the light to go around the entire watch. In my opinion, this makes the Ernest Borel flash a much more sophisticated watch when compared to the Tourist Everlight.

The only problem with these awesome watches is that their complication is based on electronics rather than mechanics. The batteries in these watches can leak after some years, and this is always a point of attention when buying one of these. Furthermore, the batteries on these watches are almost always broken / empty after such a long period of time. The chargers are also incredibly rare and thus most of these watches are sold without the lighting system working.

While these systems can be difficult to fix, it isn’t impossible. The author of the previously linked fratello articles managed to find a watchmaker capable of fixing the lighting systems. Not all watchmakers may be able to do this, but if you can find one of these watches in working condition, or if you have one fixed, you truly have a conversation starter on your wrist.