It is often required to toggle the case of current character in Vim. Vim has lot of other powerful commands related to changing case of characters, but command for toggling one (or more characters) is most frequently used and easy to remember.
Toggle current character case
## You may need to use [SHIFT] to enter ~ [ESC] ~
Toggle case of multiple characters
To toggle case of next 5 characters.
## You may need to user [SHIFT] to enter ~ [ESC] 5~