You pose a difficult question as ideally everything should be kept however it all comes down to what space you have to store these items.
Much of the stuff I list below should not take up too much room.
Basically all electrical items for starters.
Light have been mentioned
Instrument cluster
Steering column switches
All other switches / etc.
Engine ECU
Key Control Unit
All sensors - engine, ABS, etc, O2, .....
ABS unit
Airbag Unit
Airbags
Injectors
Fuse boxes
Go WILD!
......
Now this will upset/hurt some as it is butchery but:
Either remove the whole/all cable looms or cut the loom up removing all the connectors as far back as you can from where they originally attached. e.g. light, ECU, injectors, sensors, instrument cluster etc. These end connections can be difficult to find/replace when needed.
For mechanicals/body then:
Door handles!
Glass (side & screen)
Ignition switch, door locks etc. (keeps all keys/fobs as the go with the ECU & key control unit)
It is not nice to have to strip and then scrap a car but you have to mean and brutal.
When I said go wild you have to. Go OTTto begin with because when the remaining chassis is taken away there is no going back for seconds or if there is you will have to pay stupid prices.