Each skill except for Appraise, Linguistics, Craft, Perform, and Profession corresponds to a core feat that has no prerequisites and grants +2 to two skills or +4 if you have 10 or more ranks. Those feats are:
- Acrobatic: Acrobatics and Fly
- Alertness: Perception and Sense Motive
- Animal Affinity: Handle Animal and Ride
- Athletic: Climb and Swim
- Deceitful: Bluff and Disguise
- Deft Hands: Disable Device and Sleight of Hand
- Magical Aptitude: Spellcraft and Use Magic Device
- Persuasive: Diplomacy and Intimidate
- Self-Sufficient: Heal and Survival
- Stealthy: Escape Artist and Stealth
There's also Prodigy, which lets you pick from two different Craft, Perform, or Profession skills.
Beyond this standard list, there are a few feats that have a similar effect and either stack on top of the same skills (such as Uncanny Alertness, which grants bonuses to Perception and Sense Motive like Alertness) or apply to a skill pair that is not covered by an existing feat (such as Oracular Intuition, which grants bonuses to Sense Motive and Spellcraft). Voice of the Sibyl is kind of similar, although it doesn't quite fit into the same pattern.
What other feats follow this +2/+4 to two skills format? I'm looking for Bluff/Diplomacy in particular because I'm considering creating a feat for that pair. I'm concerned that it may be too powerful since it can be taken in conjunction with Deceitful and/or Persuasive as an easy way to pump those skills. Is this actually efficient enough that such a feat would be overpowered? What about other overlapping feats such as Stealth/Bluff or Perception/Survival?