D&D 3.5 Build in need of a review.

[Nosta]

The build in Question is a level 12 Human fighter. The Build is based on AOO and the use of a reach weapon.

The stats before Items or other things that Boost them are as follows

Str 16

Dex 18 + 2 stat points = 20

Con 15 + 1 stat point = 16

Int 14

Wis 10

Cha 14

14 feats from level classes and flaws
including the following Exotic weapon (great-spear), combat Reflexes, short half, Stand still, weapon focus (great spear), long reach , Robilar's Gambit, Evasive Reflexes, Knock-Down, Combat Expertise, improved trip, mage slayer, Martial study (Devoted spirit maneuver that I still need to choose) Martial stance (thicket of blades)

Items on hand.

Ring of Evasion, shadow cloak, Boots of big stepping.
The DM is giving me my great-spear as a special character boon so i'm not sure what all it will do.

I have about 66000 gp to spend yet

[AnimeTheCat]

Well, because of how high your Dex is, I would recommend putting some gold in to an enchanted Studded Leather armor. It will maximize your Dex bonus to AC. Or an animated shield so that you can get a shield bonus to AC even though you're using a 2h weapon. If you've go the gold for it both. If you can get a +2 Studded Leather Armor you will have a 20 AC and if you can get an animated Heavy Shield you will have a 23 AC. Armor will run you about 5k, shield will run you about the same. Those are just a few ideas for how to spend your gold.

[Immabozo]

Do you have LA buyoff? Do you mind LA/RHD?

[Divide by Zero]

Drop at least two Fighter levels for Crusader levels (make sure you take the second Crusader level at or after level 8). You'll lose a bonus feat but save two feats on Martial Study/Stance, so you come out one ahead, plus you'll get some more maneuvers and a bunch of other goodies.

[Red Fel]

Pity you're playing a Human. I happen to love AoO builds that use Ironsoul Forgemaster, but that requires Dwarf. In addition to crafting your own weapon - and putting whatever you like on it - your hits have a chance to daze living opponents. Yes, daze (http://www.d20srd.org/srd/conditionSummary.htm#dazed), a status that robs enemies of their actions. Your weapon can do that on-hit.

Make an AoO-happy build - Crusader is recommended - and take 9 levels of IF. If enemies attack you, make an AoO. If they attack someone else, make an AoO. If they move through your space, make an AoO. If they look at you funny, make an AoO, and they will get dazed eventually.

[ExLibrisMortis]

Drop at least two Fighter levels for Crusader levels (make sure you take the second Crusader level at or after level 8). You'll lose a bonus feat but save two feats on Martial Study/Stance, so you come out one ahead, plus you'll get some more maneuvers and a bunch of other goodies.
Same deal with Improved Trip: two levels City Brawler (Improved Unarmed Strike) Wolf Totem (Improved Trip) barbarian will provide a feat, and makes Short Haft much less needed, too. Karmic Strike requires Combat Expertise, so it's worth keeping around, but the barbarian levels are still worth it for better skills and so on. A level in exoticist fighter can get you greatspear proficiency, as well.

To sum up:
1. Exoticist Fighter 1 - Exotic Weapon Proficiency (Greatspear)B, Combat ExpertiseB, Stand StillB, Combat ReflexesF, Evasive ReflexesF, Long Reach
2. Barbarian 1 - Improved Unarmed StrikeB, speed boost
3. Barbarian 2 - Improved TripB, Knock-Down
4. Exoticist Fighter 2 - Power AttackB
5. Exoticist Fighter 3
6. Exoticist Fighter 4 - Weapon Focus (Greatspear)B, Mage Slayer
7. Exoticist Fighter 5
8. Exoticist Fighter 6 - DodgeB
9. Crusader 1 - Karmic Strike
10. Exotic Weapon Master - +2 on trip checks
11. Exotic Weapon Master - Can AoO targets with cover
12. Crusader 2 - Stance: Thicket of Blades, Robilar's Gambit

This build has everything you specified, besides Short Haft, which you shouldn't need. When an enemy provokes an AoO that you can only take with your unarmed strike, simply use Evasive Reflexes.
This build also has Power Attack, Dodge, Karmic Strike, Improved Unarmed Strike, +2 on trip checks, the ability to AoO creatures with cover (read: through enemies), charisma to will saves (+2), fast movement (+10'), a few more skill points, more maneuvers, and a way to recover them.

P.S. If you can use the crafty hunter barbarian variant together with the CA Arcane Hunter (Favoured Enemy (arcanists)), then that's a nice thing to replace your rage with, fits with Mage-Slayer.

P.P.S. In terms of magic items, it's useful to have a cloak or vest of resistance +2 or +3, a strength & constitution booster (depending on party buffs), and a +1 mithral breastplate. Also have a look at a healing belt or belt of battle.

[Immabozo]

For 3 RHD and 0 LA, you can be an Anthropomorphic Baleen Whale, size large, +16 str, +8 con, +4 dex, +6 wis, +4 int, + 4 Cha, +9 NA, IIRC. You could also take willing deformity: tall for another 5' reach, also a few levels of nature's warior gets you another 5' reach, so that is 20' reach without using a reach weapon. I also HIGHLY recommend the knockback feat for an AoO build. Who cares what your AC is if no one can hit you because your batting them away with a +60 bull rush attempt (where you dont move with them)? PA, Leap attack and shock trooper are required for that build, so is combat reflexes.