It is not really practical to use actual blockchain coins in games.
Rather, one would tend to use either things denominated in devcoins or, even better, things that can be exchanged for devcoins.
The "even better" part is because when some glitch in your game causes players to clone their stuff, such as can happen in so many games, it is not good for the survival of the game for the game operators to have to redeem all those cloned coins one for one with blockchain-based coins.
In essence the banking in almost all games is not reliable, for example in all the web based games I have looked at not one of them used transactions that either happen in full or get rolled back and retried, so any time a hosting provider reboots a web based game there is a chance the game was part way through a transaction, which will never thus be completed, so it will be out of balance.
For example suppose a player visits a moneychanger to change goldpieces into silverpieces. instead of using one atomic transaction in which the moneychanger gains gold and loses silver while the player gains silver while losing gold there would be four separate database operations, one for each currency to remove it from the one that is parting with it and one to add it to the one that is gaining it. if the machine goes down while that is happening, maybe the player paid the gold but didn't receive the silver, or maybe both parties had what they were parted with subtracted and neither has had anything added yet, or maybe even, in code that is particularly bad for the game operator, both parties got given what they were to get but did not get taken from them what they were to part with.
So no virtually no game can be trusted to account inventory and balances so you need to turn inventory and balances into actual hard blockchain-coins at an exchange/market so that if suddenly all items and currencies owned by all players got doubled it would not leave the game operator owing a doubled amount of hard coin to the players, instead it would simply lead to the market prices of the things that got doubled tending to fall somewhat as players sell off their duplicate copies of everything.
However one could put Chaumian blinded cash tokens, cheques, teller's cheques and such into games as items players can pick up, since such things if someone already cashed them they are worthless. The only way a player finding one of a many times cloned cheque or Chaumian cash token can know it is still valid is to try to cash it in at a server. (I am thinking Open Transactions style here for example) so those kinds of things could be used, in which each individual one a player has is a separate distinct serial-number kind of thing that either has or has not already been cashed-in by a previous owner.
-MarkM-