I was thinking of a promo for a game but I'm pretty sure that it's not too hard to edit the save files of games. So there's no point giving prizes (as in manually sent BTC) to just the highest scorers, as they may well be manipulated.
I was thinking of (manually) recording everyone in the scoreboard as having one ticket and those in the top places might get one or two more tickets themselves, then using a randomiser to determine the ticket. That way the highest scorers get a bit more of a chance, but if the score is a manipulated one, they don't just auto win because of that.
Thought I'd put this out to the quasi quorum of the construct community to see if you had any different methods that come to mind?