I don't know what the halacha is, but in most offices that would be considered very antisocial behavior. Babies get reprimanded when they take another child's toy, even if they are using a toy that doesn't specifically belong to anyone. (eg. at the babysitter, Dr.'s office, playground). That's training for learning boundaries in adulthood. Somebody who decided they were more entitled to a coworkers chair, stapler, pen, computer etc. would not be seen in a positive light in most offices. The supplies belong to the company, but that doesn't mean that it's a free for all to grab what you want at the expense of others.