I can't believe I am even replying to this
If there is no regulation that prohibits you carrying something on board AND your Ops Manual does not prohibit it then you can use it. Have a think about what you would be allowed to carry through normal security screening as a passenger and you won't be too far off the mark
I have discussed with company management about taking certain personal kit and they have assured me that I would face discipline proceedings if discovered.
clothing
torches
personal pens
nav computers
You must work for one scary company if what you stated is true?
However there is a one common theme in your messages
personal GPS equipment
So I wonder if this is your real reason for posting?
The answer to this one is quite simple as well. As long as it isn't forbidden in your Ops Manual AND as long as you do not plug said machine into the aircraft power supply then you can turn it on. How you use it after that is down to you, BUT if you use it for navigation and something goes wrong you had better get ready for the sky to come crashing down upon you
If I am wide of the mark with my GPS guess then let us know specifically what other piece of equipment you were thinking of using..
BTW, ditch the Leatherman, that might well get you into trouble with airport security!