The grumpy smiley is used as an indication that you are really upset about something very serious. There are many instances that can make you upset like losing something or having fight with friends. Use the grumpy smiley and let your friends know your disgruntled air.
The are many Facebook emoticons and the confused smiley is one of them. Both confused and unsure are used to denote that you are frazzled about something and not definite. Both the emoticons are used to show your friend that you are not sure about anything.

The frown and cry Facebook emoticons are used to show that both signify you are not liking something and you want to cry about it. If you are very much displeased with your friend’s behavior or for something that have went wrong then use the cry smiley. The frown is the gesture of anger mixed with disappointed.
Hence, the Facebook emoticons have their own meaning and they are used as required, but you should understand the meaning and use them when words cannot convey the message. Facebook emoticons are now the new craze making everyone fall in love with its advantages.