!dmc guest - current arguments: help. Can be used by everyone.
!dmc promoted - current arguments: none. Can be used by people who have been promoted by a DMC mod/admin.
!dmc mod - current arguments: none. Can be used by people who have been made into a mod by Diamond.
!dmc admin - current arguments: initialize, test: component, terminate: component. Can be used by Diamond and whiskers75.

You can also use !dmc status to see what your rank is. (that is the only un-ranked command)