I see many great new mods in this thread, with lots of nice pics. Fun to read, and modding is still very much alive on BLF! 
My mod this morning:
Last year I bought this little cheap travel clock in a local shop, out of nostalgia because these have been around for 30 years, but also because they are nicer IMO than the digital ones.

It works on a single AA battery and has a small bulb to light the display at night. But unfortunately the display lighting only works by pressing a momentary switch on the back, letting the switch go switches the light off again.

I was sure that it was a led but behold it turned out to be a mini incan bulb. The design is really 30 years old. But I guess it is also laziness, the battery is 1.5V so you would need a little boost circuit to light a led from it, that is why they still went incan.
I really want to light the display continuously, that makes for a nice beacon on the bedside table at night and saves clicking a button if I want to know the time. Having the incan bulb on all the time would drain the battery in no time, but I reckoned that a led at sub-moonlight level, which is what you want at night, should draw small enough current to have it lighted permanently.

This is the plan: a simple Joulethief circuit using a QX5252 component (ebay), an inductor (also ebay), and a 2300K 90CRI 5mm led bought from rngwn. As can be found online, this is the circuit (pin 1 is not used, it is for adding a solar panel to have the battery charged):

The current through the led is adjusted by the value of the inductor, higher value gives smaller current. As I want less than 1mA, I needed a very high value inductor, after experimenting I found what I needed: a 10mH inductor causes 0.260mA and 0.017 lumen from the led. 0.260 mA should drain a typical alkaline battery in over half a year, that is fine
. That is 45 lumen/W btw, which is way better than I expected from this circuitry at such low level.

Opening up the clock revealed what was expected, some wires coming from the battery connected to the glued-in incan bulb via the switch. The bulb was easily pryed out.

The hole for the bulb was widened with a drill to fit the 5mm led. (not shown) the new hole as seen from the clock face looks quite neat btw.

The cutout in the display cover was widened too, this was not a great job as you can see but it is nice enough.

Here is the circuitry soldered in place. The switch was left out, the led runs direct from the battery.

And after closing the light it works nicely and the illumination level seems just right to me :-).

The picture makes the illumination of the face look more uneven than in reality, in fact the illumination is very nice and better than from the stock incan bulb. I measured 2260K, 94CRI and duv=0.0017. I put in a new battery and let’s see if the runtime is indeed more than 6 months :)