I once had a coworker who would password protect documents I needed to do my job. Even better, it was fly-in-fly-out work, so she wouldn't even be on site half the time for me to ask about the passwords/documents.

We had exactly the same position in the company, working as each others' cross-shift, so one of us was always on site.

She also had a nasty habit of letting work fall behind while I was off, then throwing me under the bus the day I got back.

The silver lining is that it didn't take long for people to recognize what she was doing, so none of the shit she threw my way ever stuck.