Ideas for save-related bonuses/abilities

[martixy]

I'm doing a bunch of special rewards(kinda like minor artifacts) based on the saves.

They will give bonuses based on the hit die of the bearer(so they can be dispensed early and still retain significant usefulness later on).

For now a few good shared ideas between the 3 saves are:
One reroll/day of a save for each 4-5 HD
No auto-failure on nat1 (this seems like it should be on the higher levels - say 16-20 HD).
Evasion/Mettle and their improved variants - @6-8 and 13-15 HD
And maybe an increase of the bonus from +2 to +4 at around 12 HD
Treated as having the appropriate feat(Iron Will/Great Fortitude/Lightning Reflexes) for the purpose of meeting prerequisites - about 4-5 HD or just give the feat for free outright, since the end result is the same.

Any other ideas for similar shared properties?

And I'm thinking one special, unique ability each - ideas on those too?

[BowStreetRunner]

1/day when you roll a save roll two dice and choose one to use. If you choose the lower die you gain an additional use of this ability to use before the end of the day. (So essentially as long as you keep rolling good on your lower die you can keep using the ability. The first time you need to use the higher die the ability is used up for the day.)
1/day use your STR modifier for any save instead of the normal ability modifier. 1/day use your DEX modifier for any save instead of the normal ability modifier. 1/day use your CON modifier for any save instead of the normal ability modifier. 1/day use your INT modifier for any save instead of the normal ability modifier. 1/day use your WIS modifier for any save instead of the normal ability modifier. 1/day use your CHA modifier for any save instead of the normal ability modifier. (So for a character with only one high score they would likely only use one of these abilities each day. But for a character with several higher scores they might want to use each of those abilities once.)
Any time you fail a save this item gains 1 charge for the appropriate type of save (FORT, REF, or WILL). It can only ever carry a single charge at a time for each type of save. As an immediate action the bearer can spend 1 charge to 'take 10' on a save of the appropriate type. Instead of rolling they treat the save as if they had rolled a 10 on the die. (So most character would find some way to 'charge' this item between encounters, but if they end up making lots of saves in the encounter it may recharge itself as well. It won't be useful for those really high saves, but for moderate DCs will be quite useful as long as they have an immediate action to spend.)

[martixy]

These are simply awesome!

You're on a roll(pun totally intended) today.

They fit perfectly as a unique ability for each type of save.

Thanks.