If you have ever come across this error, its because replication has been setup on the database before and it needs to be removed before the database can be dropped.
In my case, I had the error when I tried to run the code below.
drop database TEST_FWXXX
Server: Msg 3724, Level 16, State 3, Line 1
Cannot drop the database XXX because it is being used for replication.
Please note that in this case, the publication and subscription had already been dropped. Simple to resolve, just remove the replication property on the DB by running the code below.
exec sp_removedbreplication ‘TEST_FWXXX’
After running this, I was then able to drop the database successfully.