When you're creeping on someone's Facebook and accidentally request them as the friend, usually done on mobile devices.

A much more humiliating and frustrating experience than Left on Read

In the case of Left on Request the person you're messaging isn't even aware of your existence

It sometimes can be unintentional if the person you're trying to message is bombarded by DMs all day long she or he might miss you in the list of people trying to slide into their DMs

A work request sent to help desks or administrative assistants that should be very quick and simple to complete, but comes back over and over again due to the requestor's poor attention to detail or indecisive work groups or committees unable to agree on a final version of the request.

A zombie request can also relate to non-business requests, such as requests from a honey-do list or a family member.

A request to a person(most likely a friend) for sex when you're really in the mood for it. Asking a friend to have sexual intercourse when your body can't hold in the urge anymore.

to state what you want again, because the dumb ass could not do it right the first time.

To receive a friend request from someone who is not your friend, but requests you regardless.

When you see a member of the opposite gender that you find attractive and you would like to add them on facebook.