One thing I am personally obsessive about is USB devices such as memory sticks. A malicous USB device can do all sorts of damage, just by plugging it in, but it is surprising how many people will do so without a second thought.
For myself, I will only allow such devices including memory sticks/cards etc to be attached if I have owned the device from new, and it was supplied in manufacturer’s sealed packaging, and it has never been installed in any machine I do not control.
I have sometimes found that people are offended when I refuse to plug in their USB sticks and other devices devices, but they usually get over it. Some have even come around to my way of thinking, and enforce similar policies.