Just a few ideas for prestige enhancements. To be honest I'm not sure which classes some of these would be suited for but I'll suggest them where I can.
Shadowdancer
(Rogue, Ranger, Monk)
Level 6, 12, and 18 enhancement
Level 6:
Shadowdancer I-
Requires Hide 10, Move Silently 10, and Tumble 5
Also must have Dodge and Mobility, Hide II, and Move Silently II
The player is granted the ability to become one with the shadows, gaining a +2 bonus to Hide, Move Silently, and Jump checks. The player is also granted a natural 10% concealment at all times unless wearing armor heavier than light.
The following abilities are also granted:
Shadow Meld I-
The shadowdancer is able to mix themselves with nearby shadows making them incorpreal for 30 seconds. While in this mode the Shadowdancer recieves a +2 circumstantial bonus to Hide and Move Silently checks. This ability has a 5 minute cooldown.
Shadow Illusion I-
The shadowdancer is able to mix together an illusion of themselves which will distract the target for a short time. The illusion has 1/5th of the Shadowdancer's HP, AC, saves, and skills but also has a 20% concealment bonus. If the target succeeds at a will save, the illusion is destroyed.
Level 12:
Shadowdancer II-
Requires Shadowdancer I, Spring Attack, and Toughness
The shadowdancer becomes even more attuned to the shadows increasing their checks by an additional +1, and a 15% concealment unless the player wears armor heavier than light.
The following abilities are also granted:
Shadow Jaunt-
Once per rest the shadowdancer is able to use the spell Dimension Door, except only transporting themselves.
Shadow Meld II-
The duration increases to 45 seconds and the checks increase to +3.
Shadow Illusion II-
The illusion is able to utilize 1/4th of the shadowdancer's stats instead of 1/5th. The illusion is also more difficult to disbelieve.
Level 18:
Shadowdancer III-
Requires Shadowdancer II
The player has mastered their attunement to the shadows, increasing their checks by another +1 and their concealment to 20%, restrictions still apply.
Summon Shadow-
Once per rest the shadowdancer is able to summon an undead Wraith of the same level for 10 minutes.
Shadow Meld III-
The duration increases to 1 minute, the checks increase to +4, and the cooldown drops to 3 minutes.
Shadow Illusion III-
The illusion is now able to utilize 1/2 of the shadowdancer's statistics instead of 1/4th. The will save becomes more difficult.
Blackguard
(Barbarian, Fighter, Cleric)
Level 6, 12, and 18 enhancement
Blackguard I-
Requires Cleave and Great Cleave
Also requires Tumble 5, non-good
The blackguard has made their first brush with evil and liked it. They recieve the ability to add any bonus from their charisma to their saving throws, similar to a Paladin. They also recieve a +1 bonus to AC when fighting good enemies.
Includes the following abilities:
Dark Curse-
As an Action Use, the blackguard is able to bestow a powerful curse on the target which drops all ability scores by 1 and inflicts 1 negative level. Fortitude Save negates.
Aura of Despair-
All enemies within 10 ft. of the blackguard suffer a -2 morale penalty to saving throws. This is constant similar to the Paladin's aura of good.
Summon Lesser Fiend-
Once per rest the blackguard is able to summon a Hell Hound for 10 minutes.
Blackguard II-
Requires Blackguard I
Also Requires Slicing Blow
The blackguard liked their first taste of evil and is back for more. The Aura of Despair inflicts an additional -1 penalty to saving throws and an additional -1 penalty to AC. The Dark Curse causes 1 additional point of ability damage and 1 additional negative level.
All of the following are also included:
Rebuke Undead-
The blackguard is able to make a turn check to frighten or destroy undead 3 times per rest. However, when an undead would be destroyed, it is instead commanded. The Blackguard cannot command more than 1 HD of undead per level of their highest level class. (ie. if the blackguard enhancement is put into fighter and this is used as 12 fighter/8 rogue, the player could not control more than 12 HD of undead at any one time.)
Summon Fiend-
Once per rest the blackguard may summon a Fiendish Troll for 10 minutes.
Blackguard III-
Requires Blackguard II
The blackguard has reached the pinnacle of evil, achieving powers equal to a lesser fiend. The Aura of Despair inflicts an additional -1 morale penalty to saving throws and AC. The Dark Curse causes 1 additional point of ability damage, 1 additional negative level, and lowers the target's SR by 1 level (if the target had 14, now it has 11).
Also includes the following abilities:
Evil Attunement-
The blackguard recieves a natural SR of 14 and an additional +2 to their natural AC bonus due to their fiend-like powers.
Death Attack-
Once per rest the blackguard is able to attempt a death attack against a single target. The target must make a Fortitude Save or die instantly. If the target succeeds in its saving throw, this attack still inflicts 3d6 additional negative energy damage + 3d6 if the target is of good alignment.
Summon Greater Fiend-
Once per rest the blackguard is able to summon a Bezerika for 10 minutes.
Unholy Prayer-
As an Action Use, the blackguard is able to chant a prayer to their evil deity. Any enemies who hear this chant are affected as though within range of the blackguard's Aura of Despair. Any enemies affected by both must make a fortitude save or be cursed.