USERNAME -- your login username 
Foswiki makes names available in three formats: USERNAME like 
jsmith, WIKINAME like 
JohnSmith and WIKIUSERNAME like 
Main.JohnSmith. Un-authenticated users are all 
WikiGuest.
This macro is an alias for the USERINFO macro with a fixed 
format="$username".

 The login username is considered "protected"
information by default and will not be revealed to non-admin users.
  Parameters 
     
  Examples 
 
-  %USERNAME%expands toguest
-  %USERNAME{AdminUser}%expands to ==  When used in a template topic, this macro will be expanded when the template is used to create a new topic. See  TemplateTopics for details 
REMOTE_USER, 
USERINFO, 
WIKINAME, 
WIKIUSERNAME, 
UserAuthentication