Interesting enough Jr. DBA asked me how he can get current user for any particular query is ran. He said he wants it for debugging purpose as well for security purpose. I totally understand the need of this request. Knowing the current user can be extremely helpful in terms of security.
To get current user run following script in Query Editor
SYSTEM_USER will return current user. From Book On-Line – SYSTEM_USER returns the name of the currently executing context. If the EXECUTE AS statement has been used to switch context, SYSTEM_USER returns the name of the impersonated context.