Welcome to the Browser-Base Game Zone forums!
simple flip the coin game where the player gets double the money when he wins and a random item when he looses.
What about multiplayer games like poker or black jack? These would keep the money within the economy as saljutin suggested...I think it would be easy to figure out the odds...house would always win but some good/lucky players could make money...the main advantage I see over this would be that it is more exciting...but maybe thats just me
I can send you pics of my cocks if you want reference.