For a nickname

1. As a shortened version of your name. If you have a long name, forming a nickname from it can save time.
2. To show a characteristic you possess. If you're quick on your feet, you might get a nickname like Speedy.
3. As a reference to some past event. Sometimes, you receive a nickname because of something you did or had happen to you. This is usually known only by a certain group.
4. A title or rank can be become a nickname.
5. A last name can be a nickname. Sometimes you may prefer to be called by your last name.
6. A nickname could reveal something you like. It could be your favorite color, food, or even an animal.
7. It could be a pet name. Some common ones are Sweetheart, Darling, and Honey.
8. It could be used as friendly teasing. Just be sure that everyone involved is alright with the nicknames given. It's not friendly unless everyone is happy with the nicknames.
9. As a filler name until you can learn their real name. There are times when you don't know someone's name, but need something to call them. These are usually temporary, but can end up becoming an oft used nickname.
10. To hide an embarrassing given name. Sometimes, people can find the name that they were given by their parents to be embarrassing. At such times, they may decide to create a nickname that they find to be less embarrassing.