USB soldering iron

Cheap (under $5) 5V/8W soldering iron.

 Cable length = 150cm. This is not silicone, but still way more flexible than any mains cable.

 Tip with integrating heating element is interchangeable. These cost ~$1.20, but apparently only this tip style (cone) is available. Heater seems to be located very close to the tip.

 NE555 is working as monostable trigger, being turned on for 30s with either touch sensor (metal bump) or shock sensor. Heating up is really fast, as advertised - less than 15 seconds.
Iron heats to temperature over 400C - more than I would like and Sn-Pb solder on the tip is oxidizing quickly. At the same time this is not powerful enough to e.g. melt Pb-free solder on mounting pin of USB-A socket connected to ground plane.

 MX35N06

 Shock sensor is just tight metal spiral inside aluminum tube. It doesn't seem to be too sensitive, it is also fragile - connector wire breaks easily when bent.

 Most switching power supplies have some leakage, being able to light neon voltage probe connected to output. In this iron tip is directly connected to +5V supply rail. This might create risk when soldering ESD-sensitive components. It also seems to cause problems with touch sensor as my iron wasn't going idle at all even when lying.
Alternative method of reducing excessive sensitivity of touch sensor might be putting small capacitor (I've tested 510pF positively) in parallel to D1 diode.

To get rid if leakage I've assembled simple adapter consisting of USB-A plug, USB-A socket and crocodile clip on a cable connected to +5V line. Inside crocodile clip there is also resistor - 33k or something like that as I would prefer no direct connection to the ground in case I would use it on powered circuit. I'm attaching this clip directly to ground pole of mains socket. Using separate mains plug to connect to ground line would be safer and more reliable, I hadn't have one at the moment though and this would also require availability of extra mains socket.

I probably would not recommend it as first and/or only soldering iron for anyone, but it works for me acceptably as secondary/extra soldering iron I'm keeping at workplace for small tasks like soldering some thin wires and replacing few SMD resistors, capacitors or transistors. Quick heating up is a big plus in this use scenario.