The lone from Glasgow to Kilmarnock and then onto Dumfries via Sanqhar ( my apologies I don't know the name of that line ).
But it's a fairly major line , which despite Scotland leading the way in electrification, has so far been ignored .
Also the highland mainline. , from Dunblane to Perth and Perth to Inverness and Aberdeen , and in turn Aberdeen to Inverness.
Of course with incoming bi or tri.mode locos ( class 93 and 99, also existing class 88's) or the odd decision not to make the pretty good class 395's part of the same A train family that makes up the Intercity fleet's, class 800, 802,3,5,7 and 10's .
These do mitigate the lack of wired sections of course .
Other notable gaps is the phase 1 and the current phase 2 east west rail ( phase 2 being Oxford to Bicester, that saw a new station and improvements at Oxford , now the next phase to Bedford vis Bletchley or the spur to Milton Keynes and beyond Most of this reopening , has some provision for electric running, but ingather they left many older bridges untouched, if course they could just replicate the ideas from the western mainline to south Wales, where gaps were left , due to costs.
Seemingly trains ' coast , through such gaps .
Also the south Humber line to all the freight terminals like Immingham , but also serving all stations to Scunthorpe, especially for freight , where electric traction would improve the line and allow better trains , than the dreadful class 150's and 156's . But then there are plans for Northern , And Scotrail to order full fleet replacements.
Anyway the south Humber line , meets with the line via Brigg, kirton in Lyndsay, a sizeable place that would benefit , that goes to Gainsborough and onward to Lincoln or Doncaster and the ECML .
Also the mml via Sheffield to Link up to the electric ECML , again would be very useful, and if linked to an electrified line from Sheffield and Derby, toward Burton in Trent to Birmingham and Bristol direction , would potentially offer , more competitive services, than the current, cross country operation , that removed longer and well lijed HST with tiny 4 car voyagers .
Again if it was wired , it would provide scope for better services.
Add all this to reopenings elsewhere like Leven in Scotland where it was promised to be electric from the start , they have built foundations for masts and some places on that line have visible piles poking out of the ground.
So again the fife circle and line to Edinburgh across the bridge to link to the electric lines from Glasgow , would be useful .
I'm sure there are many more , including reopenings .
All are needed as the terrible electric cars won't have that freedom of motoring that lead to the decimation of our rail network in the 60's , now we are almost full circle and more railways will be needed , and thus electric traction, for a greener operation.