After much deliberation I dont think this is a good idea. I think OP is in good intentions, but there is no way for us to verify that he isnt lying about this to gain attention.
It would be fairly irresponsible of us to allow someone to bait people into this "contest" with the chance that he tells whoever wins to take a walk at the end. Could be a very elaborate and successful troll.
I was torn about this decision because I did something similar last year where I gave away two subscriptions to Game Informer just before the big November Reveal in a riddle thread. So I have been in OP's shoes.
But what I can say the OP can do, if he so desires, is create a signature for his profile detailing the rules for his "contest" and requesting members to PM him about it. This way everything is dealt with privately instead of publicly.
I appreciate all parties involved understanding my position on this, and hopefully OP sticks to his word and gives away a free copy of GTA V one way or the other.