I've got a nostalgic view of hero points from my time playing Deadlands with my first game group almost two decades ago. For the games I run, I try to adapt fate chips from that system to the one I'm using. Here is the result of my efforts to bring Fate Shards to the Pathfinder Playtest.
At the start of every session, each player will draw three shards from the Fate Pouch, and the GM will draw one shard plus one shard per player. The GM always draws last. Any shards left over at the end of a session are saved and recorded on the player's sheets. These saved shards are drawn out before everyone's normal draws.
There are four types of shards: Minor, Moderate, Major, and Miraculous. The Fate Pouch starts with 24 Minor, 12 Moderate, and 6 Major shards in it. The Pouch does not start with any Miraculous shards, though those can be added during the game.
Miraculous shards are added whenever the group accomplishes some significant deed. Unlike other shards, they are also removed once used, so they can only be used once. The GM must exchange a Miraculous shard for a lesser shard of their choice from the Pouch when they draw one.
You can use a shard on your turn as a free action, or as a reaction when it's not your turn. When you use a shard, you cannot use another until the start of your next turn.
Shards can affect your actions, or the actions of enemies that would affect you. Describe what is happening to change the outcome (remembering your training, just blind luck, divine intervention, etc...), and apply the desired effect from the options available.
You can use an equal pair of shards to apply the fate effect to an ally instead of to yourself. Using a pair of shards in this way counts as using a shard, and you still cannot use another shard until the start of your next turn.
Any shard can always be used as if it were a lesser shard, including counting as an equal pair for applying the fate effect to an ally. A Miraculous shard that is used as a lesser shard is only discarded - it is not removed from the Pouch.
Some events are predestined and most shards of Fate cannot change them. Shards cannot force rerolls of natural 1's or natural 20's, and they cannot reduce damage from actions involving those rolls. Miraculous shards ignore this rule.
The effects of each type of shard are as follows:
Minor Fate Shard : (1) Use this shard to reroll one d20, or force an opponent to reroll one d20 against you. The second roll must be taken. (2) Use this shard to immediately take a Step action. You can use this as a reaction after any opponent's action has finished. (3) Use this shard to suffer only half damage from an effect.
Moderate Fate Shard : (1) Use this shard before any d20 roll to roll twice and take the better result. Can also be used against an opponent to make them roll twice and take the worse result. (2) Use this shard to immediately take a Step or Stride action. You can use this as a reaction to interrupt an opponent's action; if this move takes you outside the range of your opponent's action, it does not affect you. Alternatively, you can use this reaction if your opponent would move out of your range to follow them and complete your action. (3) Use this shard to take no damage from a single effect.
Major Fate Shard: (1) Use this shard after any d20 roll to roll again and take the better result. Can also be used against an opponent to make them roll again and take the worse result. (2) Use this shard to immediately take an extra action on your turn (increasing your total actions that turn from three to four). Alternatively, use this shard to take an additional reaction between turns. This can be a reaction you have available or the Step or Stride reaction from the Moderate Fate effect. (3) Use this shard to ward off death. When your character is dying or would die, use this shard to instead recover some HP (Level + Con Mod) and regain consciousness. However, using this effect discards all your other fate shards.
Miraculous Fate Shard : (1) Use this shard to increase your check result by one step (critical failure > failure > success > critical success), or to decrease an opponent's check result by one step. (2) Use this shard to immediately take an additional turn. This can be used as a reaction to interrupt an opponent's turn. (3) Use this shard to give a Major Fate effect to you and all your allies. Each ally chooses the effect to receive. They can spend these effects immediately or during their next turn.