You guys could point me a better option though.. The idea behind this game is to select a winner (or more) from a list of particpants. The game would announce something like: "we are at block 568903 - result at 569000 (using nonces as seeds from block 568996 to 569000)"
Using multiple blocks would avoid nonces comming from only a miner, right?
I think there are two commonly used approaches: The first is to use the block hash instead of the nonce. This way, it is way harder for a miner to manipulate it - but they still can if the game is worth really a lot of money. Basically when they have solved a block but do not like the outcome of the game, they can decide to not publish the block and try again. But that loses them a block reward - so is only worth it if your game is about more money than that.
The second is using a hash commitment - like what @ETFBitcoin proposed above. You can have all participants of the game create random numbers and publish the hashes. Then you base your game outcome on some combination of the numbers themselves (which the players have to reveal after everyone published their hash). This ensures that noone knows the outcome (or can manipulate it) before the hashes are revealed, but also noone can change their number afterwards since that would invalidate the commitment.