A better approach IMHO is to turn them into PUTs. If something would normally be a POST but you've eg used GUIDs to ensure that creation actions are idempotent, then such actions should be PUTs.
But then again, some things must not be idempotent: eg "shuffle this deck of cards in an order that is random to me".
Edit: On second thought, you could make that idempotent too, albeit at the cost of increasing server load and your app's architecture's complexity -- you would just have to verify that the deck has had some reordering since that client's request, and not make any further reorderings in response to that client, since from their perspective it's still randomized.
But then again, some things must not be idempotent: eg "shuffle this deck of cards in an order that is random to me".
Edit: On second thought, you could make that idempotent too, albeit at the cost of increasing server load and your app's architecture's complexity -- you would just have to verify that the deck has had some reordering since that client's request, and not make any further reorderings in response to that client, since from their perspective it's still randomized.