Club Nintendo in Europe are running a “Monster Hunter: Gift & Hunt Together Promotion”.
If you register the Nintendo 3DS version of Monster Hunter 3 Ultimate with Club Nintendo before 10:59pm (UK time) on June 30th, you’ll receive a recommendation code, which you can pass on to a friend.
Then, if your friend registers a Nintendo 3DS or 3DS XL system between 11:01pm (UK time) on 3rd June and 10:59pm (UK time) on 31st July 2013, and enters the Recommendation Code before 10:59pm (UK time) on 5th August 2013, he or she will be eligible to receive a free Download Code for Monster Hunter 3 Ultimate on 3DS.
If you already happen to own Monster Hunter 3 Ultimate and have registered it with Club Nintendo Europe, the Recommendation Code will become available on the Club Nintendo website from 3pm (UK time) on June 3rd.
More details on the promotion are available here.