So I love theory crafting/character creating in Pathfinder and yesterday I experimented on a Tank build (AC and HP focused) and came up with this:
Spoiler: Tank Min-Max
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Tank Build - Fighter lvl 1
Optimized Tank Build

16 Strenght +3
14 Dexterity +2
18 Constitution +4
13 Intelligence +1
10 Wisdom +0
10 Charisma +0

Feats:
Combat Expertise (+1AC*)
Shield Focus (+1AC)
Dodge (+1AC)

BAB: 3
AC: 25
HP: 14
CMB: 4
CMD: 18
Fort: 8
Ref: 3
Will: 0

Chainmail (+6/+2/-4)
Tower Shield (4AC)
Arming Sword (1d8)

This Build only utilizes the CRB, with average stats and barely costs 200 gold to start with.
Now I'm not saying that I need help with my party, me and my mates aren't powergamers and we don't abuse the system overly much, but I'm curious how experienced DM's deal with such pest's. The way I see it this character build is practically invincible to everything but critical strikes and magic missiles, with maybe the exception of the occasional Combat Maneuver. (which will always result in AoO on the opponent on low levels) Only weakness I see, is that the characters is slow in medium armor, but give him a crossbow and that problem is solved also. (for running away opponents)