Obviously as is true in all games, many of us will house rule certain parts of the game for our play group.
These are mine in regards to use of Willpower:
Player and Game Master Rule
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When you would take damage from rolling 1s on stat dice you can spend willpower one for one to muscle through and press on taking no damage. You must be able to spend enough WP to soak the damage from all 1s. You do not gain willpower.
(This basically allows players to trade off getting Willpower for not taking damage. Its not usually used in combat builds but non combat builds make use of it semi regularly. On a GM it just allows me to push NPC threats further, which considering stock npcs quickly end up underpowered compared to pcs, it maintains them as a threat)
Game Master Only Rules
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Spend a WP to push a monster attack roll, or a monster armor roll
(as these are rolls that technically cannot damage the monster, I don't allow them rerolls on them)
Spend willpower to roll additional dice on an attack (treated as a skill die).
(I don't want to make it just auto damage, the luck is part of the game to me)