I would definitely put the key to good use. Been around the block when it comes to gaming and betas. As far as games tested that i've been a part of i'll and list the games according to date that I can remember.
Shadowbane: Closed/Open Beta - March 2001
Neocron: Closed/Open Beta - October 2002
Lineage 2: Closed/Open Beta - November 2002
Planetside: Beta - January 2003?
Guild Wars: Open Beta - December 2004
Ferentus: Open Beta - November 2005
Darkfall: Closed? 2008
Guildwars 2: Closed 1 December 2011
Path of Exile: Closed September 2011?
Diablo 3: Friends and Family to Closed 2012
Planetside 2: November 2012
Firefall: Closed Invite Only March 2013
There are a few other games that I know I missed but this is a good chunk of them. Anyways, I hope I get a key soon, looking forward to playing!