After a 3 day hike and dinner, we ended up at Visalia Airport on monday night (July 3rd) around 20:15. I went to preflight the plane after we had just dropped the rental car keys in the Enterprise lockbox.
Small problem: the motor would crank as soon as the master switch came on (key was not even in the dashboard).

I elected to start the engine, which went ok, and tried to see if by any chance it would disable the cranking.
I looked in the POH for the crank motor diagram and it doesn't show any fuse unfortunately (that's lame, you'd think that there would be a disable fuse for that)
The ammeter showed a charge, which is what I expected with the alternator running and I then came to guess that the crank motor had stopped, otherwise I would have gotten a discharge. I found out later that this assumption was incorrect and the ammeter didn't actually include the starter motor draw, so the alternator was likely charging the battery while the battery was discharging 10 times faster trying to keep the crank motor running (there as no good way to know that it was still actually running)
So, I continued preflight, but a short time later, the avionics go dead. Sure enough, the battery died and the crank motor must have still been running.

The engine was still running of course, and I'm now on a taxiway with no lights, no avionics, and thinking what will happen if I shut the engine down:

• stuck in a deserted airport
  
• no car since I just gave the keys back and there is no one from entreprise that could be called at this hour
  
• even if I slept overnight, the next day, July 4th, didn't seem like a great day for getting a mechanic in a deserted place. Even enterprise where I dropped the keys would be closed too, so I couldn't drive home.
  
• just to make matters better, I had a surgery scheduled 2 days later, and I really didn't want to miss it as I had been waiting for it for months
  

I also had with me:

• one handheld GPS that was already setup to point towards PAO
  
• 2 handheld radios, one NAV capable
  
• several battery powered lights
  

Against me:

• I wasn't feeling my top
  
• it was dark
  
• no landing lights, nav lights, or flaps
  
• no xpander for Charlie transition or ducking under Bravo towards PAO
  
• And let's say it, it would have been hard to justify that this flight would have been legal
  

Like any pilot, I have been trained in flapless landings and had just done a few a few days prior, and also had trained in light-less landings. So, if you add the additional handheld avionics I had (I was really only missing a transponder and navlights), it was very tempting to go instead of being stranded in BFE over July 4th and likely miss my surgery on the 5th.

The temptation to go home was strong, but in the end, just too many things were stacked up against me, and I especially did not like the fact that I had no engine gauges working (fuel / CHT / EGT / oil) to warn me of any separate problem that could have happened. I also really didn't like the idea of gliding to an emergency field at night with no lights and a handheld radio. And of course, doing that flight wouldn't have been legal anyway, so I taxied back to parking.

Luckily, at least I had a bunch of hardware and toys with me, starting with a new cell phone battery, which allowed me to call a coworker, who nicely agreed to come pick us up the next day. Turns out however that I didn't have to call on this favour as I had even more luck: a pilot had just landed and was tying down his plane. He was nice enough to drive us to the closest hotel, pick us up the next morning, and fly us to PAO (he was too tired to do it that night, which was fine with me).
I got to fly a portion of the flight in his 180hp V-tail Beech B35. Weird beast to say the least (3 separate fuel tanks, one fuel gauge, and no electric fuel pump), but lots of payload apparently (4 people plus 120lbs of luggage in the back)
A few pictures are here

The faulty C172XP is still sitting at Visalia, waiting for a mechanic to fly over, or being looked at by a local mechanic, but at this point, it's not my problem anymore :)
Too bad this 172XP seems to have a few quirks like this, because it flies a great 130-135kt, had good payload, and is only $112/h (quirks = broken fuel and CHT gauges during my last 2 flights in it, although they have been fixed)