One of my favorite podcasts, High Rollers (sadly stuck in Hasbro Hell) uses "fate dice", a set of d6s rolled at the start of each session, that can be used by the players (high rolls) or the DM (low rolls) to influence other rolls and situations, but doing so moves the die into the opposite pool.I do wish both sides interacted with them more though. It's a cool idea.I think they got used the most during the window of time when the DM let the players spend them after seeing a roll (but before knowing the result). They get squelched by forgetfulness and what-if-I-need-it-later-itis.Sure, adding them then probably ruins the balance, but fun is more important than balance.