Feat Synnergy and You.

[Timeron Malachi]

I play a lot of fighters, so I definetly like the idea of feat synergies. I'd have to think about them for a bit to really come up with any, though.

With Combat Reflexes, I'm pretty sure you get an attack of oppurtunity anyway.

 

[Save-vs-DM]

Okay, this is certianly a super nifty idea, so I'm hear to add my thoughts to this. I started alphabetically, starting with the rather underwhelming feat Combat Casting.

Combat Casting Synergies

Combat Casting + Blind-Fight: When casting on the defensive, you gain an additional +2 bonus on your concentration check to cast a spell defensively against unseen or hidden opponents.
Combat Casting + Dodge: When you declare the target of your dodge feat, you receive an additional +2 bonus on concentration checks to cast a spell defensively against the target of your dodge feat.
Combat Casting + Deflect Arrows: You receive an additional +2 bonus on concentration checks to maintain or cast a spell when you are hit with a ranged weapon.
Combat Casting + Mounted Combat: When attempting to cast a spell on horseback, you receive an additional +2 bonus on concentration checks made to cast spells while mounted.
Combat Casting + Spell Focus: When attempting to cast a spell defensively, you gain a +2 bonus on your concentration check provided the spell being cast is of the same school you have Spell Focus in.
Combat Casting + Toughness: The DC of your Concentration check made to cast a spell while being damage is 7 + damage dealt, instead of 10 + damage dealt.
Combat Casting + Magical Aptitude + Shield Proficiency: Your arcane spell failure is treated as 5% less for any shield that you wear.

More to come later.
Save vs DM

 

[Save-vs-DM]

Not to leave the fighters out, here is what I came up with for Combat Expertise

Combat Expertise Synergies

Combat Expertise + Blind Fight: When using Combat Expertise against an invisible or unseen foe, your dodge bonus to Armor Class improves by +1 against all unseen or hidden foes.
Combat Expertise + Dodge: When using Combat Expertise and Dodge in the same round, you may choose a number of additional opponents for your dodge feat equal to the penalty you take on attack rolls from the Combat Expertise feat.
Combat Expertise + Diehard: When you are at -1 to -9 hit points, you dodge bonus to Armor Class when using Combat Expertise increases by number equal to your negative hit points. (I.E. if you are at -3, then you gain an additional +3 dodge bonus to Armor Class).
Combat Expertise + Great Fortitude: When using Combat Expertise you gain an additional +1 bonus to Fortitude Saves equal to one half the dodge bonus granted by Combat Expertise.
Combat Expertise + Iron Will: When using Combat Expertise you gain an additional +1 bonus to Will Saves equal to one half the dodge bonus granted by Combat Expertise.
Combat Expertise + Lighting Reflexes: When using Combat Expertise you gain an additional +1 bonus to Reflex Saves equal to one half the dodge bonus granted by Combat Expertise.