Just some ideas,
How about a polearm user? Spear, Heavy Poleax, Dwarven Warpike, etc. Choose something which could be readied against charge. Then buy steadfast boots. With appropriate feats like Combat Reflex and Hold the Line, you can be a real guardian of entire party. Cleave work very well with those weapons, too.
It seems that there is no full-level cleric in your party. It is always good to have a pure cleric.
There is no fighter/mage type in your party. As your party already has 2 arcane casters, you may make heavily melee-oriented fighter/mage build which uses Arcane Strike feat or Wraithstrike spell intensively.
Warlock could be another option. That class is not as versatile as other spell casting classes. But good at fighting. As your party already has enough spellcasters, you can go for it.
If allowed, large race such as Half-Ogre could be quite different from other characters, too.
As your party already has enough characters, you can always enjoy to be a monk or bard
Edit: And, as your party is relatively big, a character who can enhance entire party, such as bard, marshal, outcast champion, etc., could be really good, too.