Just my 2.2c worth, I tried vaseline, couldn't find anything else light, for years but as others warned it turns into a gunky mess soon after.
Lately I've tried PTFE (teflon) dry film lubricant which works well. Can buy it from auto shops.
I think, keep away from silicone lubes around electrical contacts as it is an insulator and can be hard to remove from contacts.
That's a fair point arcadoz, ptfe is better than using normal grease for lubricating gears and shafts - but don't use it on plungers.
