Workplace Snitch

A person that looks for any opportunity to report any bad behavior by other employees to management whether true or not. In order to curry favor for preferred work assignments or for possible promotion.
People like this are usually very insecure and have low self-esteem. They always want management to think of them as their best employee. So if they see another employee that is "better" than them. They will go out of their way to discredit them to management by making them appear lazy or incompetent.