Everyone know Leadership is the most powerful feat as it gives you another character. But you can equally abuse the followers you gain aswell. So I present
The Tsunami ArmyBuild: Take Leadership at level 7, have a high charisma.
When you reach a leadership score of 25 or higher you have 163 followers, say they are all Clerics, Oracles, Druids, Inquisitors or even Adepts. They all take
Allied Spellcaster, the cantrip
Create Water,
Gifted Adept trait for Create Water and for the level 3+ Spell Focus (Conjuration) and
Bloatmage Initiate.
Go to some stragetic point in space (on the side of a mountain, in the middle of the air, on the other side of a Gate or the like) and get them to all cast Create Water. With a minimum caster level of 3 on your 1st level casters and a maximum of 9 on your 6th level casters you will be creating 1122 gallons/round of water. For added devastation make a basin out of a wall of X or fabricate one and dump the water all at once.
Wipe out cities, drown those pesky drow or even water the crops in a time of drought all with a cantrip. In context this is some real world numbers:
It would take 58 minutes and 9 rounds to fill an olympic swimming pool.
If they worked 8 hours a day they would provide water for 15,386 average American Households:
This is also using a conservative reading of Allied Spellcaster, if you can get the +1 caster level more than once for being adjacent to more than one ally this number gets stupidly big.
This is just using Pathfinder sources (including 3.5 this number can be dwarfed easily) but I am quite sure this number can be higher. Are there any caster level shenanigans in Pathfinder that I have missed?
Edit: Thanks to Halinn for directing me to the Gifted Adept trait and Maat Mons for the real world numbers.