Lightning Conductor
by Kitkat

See also Fluen's Lightning and Electric Arcs tutorial

The LIGHTNING_CONDUCTOR item produces a vertical blue electrical current effect (like the electric arc produced by FLAME_EMITTER3) and can be found in the Street Bazaar level lowstrt.tr4.

OCB 0 makes the lightning effect non-fatal.
OCB 1 makes the lightning effect fatal.
OCB 2 makes the lightning effect not appear even if it is triggered.
OCB's 3+ makes the lightning effect non-fatal. 

To add the 'lightning' sound:

In Wadmerger -

Find THUNDER_CRACK
Press 'Add'.

In the SFX file - 

Find the thun_crk sound in the sounds.txt file.
Add a space then #g to the end of the line.
Save the file back on itself, then run the SFX example.bat file.

Points to be aware of:

The nullmesh must be placed on the floor of your room for the strongest effect.

There doesn't seem to be a way to control the timing of the lightning conductor.

Be careful when placing other rooms nearby as the lightning conductor effect may affect them too; similar to having 'bubbles' in rooms adjacent to water rooms.