I am currently in an all mage group, and maybe I have watched too much anime but, I was wondering if there is any feat that would give us a bonus if multiple mages casted the same spell together. I just have this awesome image in my head of our group all casting fireball at the same time and having a huge explosion.
Sadly, Pathfinder has little to no support for cooperative casting. I had to make some fairly extensive house rules to justify the existence of some higher level magics in an otherwise moderate magic world.
The only teamwork feat that goes a little in that direction is Allied spellcaster. Another one that might help if your wizards are wearing bucklers/light shields (possible if mithral) is shielded caster.
Alllied Spellcaster isn't bad. Unfortunately, I don't think it scales to allow more than one bonus per spell, so no ridiculous fireballs from a gaggle of low-level wizards.