Here's a list of all Codes ZQ handed out. Some are no longer available. Sorry.
All codes should now work with the Demon Campus update.
Facebook event 1 : No longer available.
April fools day(only works during the event)(can't use anymore)
Facebook event 2 : No longer available.
[Edit 23 Apr 2014]: Code "zqknights" has been reset and can now be used a 2nd time.
[Edit 26 August 2015]: All four freebies have been reset after the merge of Evanstone, Grodo and Hasgroth.