Good news for those that have yet to buy Guild Wars 2 but want to try it out! On November 12th, ArenaNet will implement Refer a Friend Free Trial:
To do so, you need a Guild Wars 2 account in good standing that was created before 23:59 PST (7:59 GMT) on November 6.
We will give you more details once the program goes live, but start thinking about who you want to invite! [Source]