3.5 making an effective greatspear combatant

[King-Strawberry]

The greatspear is an exotic weapon in comple warrior, anyone have any builds or advice on making it usable?

[BowStreetRunner]

It's a 2d6 piercing reach weapon with a x3 crit and a 10 ft range increment when thrown. Unless you are building around using all of those properties, you are probably wasting a feat on exotic weapon proficiency. Consider:
A longspear is a 1d8 piercing reach weapon with a x3 crit. So by comparison your feat nets you an average of 2.5 damage and a 10 ft range.
A spear is a 1d8 piercing weapon with a x3 crit and a 20 ft range increment. So by comparison your feat nets you an average of 2.5 damage and a 10 ft reach, but a reduction of 10 ft range.

Basically, unless you are building around the reach and range increment, I can't see this being worth the feat. The extra damage isn't worth it - there are feats that can yield a lot more damage on average.

[Splendor]

Shorten Grip Feat (Dragon 331) allows you to take a -2 to hit with a polearm to attack adjacent foes.

Shield and Pike Style (Dragon 338) allows you to still get light shield bonus to AC when using a piercing reach weapon.

If I was wasting a feat on an exotic weapon I would take the heavy poleaxe instead. Yeah I can't throw it, but I hardly ever throw my main weapon at someone. The Hvy poleaxe does the same damage, same crit range but its a slashing/piercing weapon instead of just a piercing weapon. It also considered a halberd for all feats (Complete adventurer pg 116)

Fighter
1st) Exotic Wp Feat
F1) Shorten Grip Feat
Flaw) Combat Reflexes
Flaw) Wp Focus Feat
F2) Shield and Pike Style
3rd) Two Weapon Fighting
F4) Wp Spec
Lv 6) Spinning Halberd (C. War)
F6) Hold the Line (C. War)

This setup allows you to attack anyone within 10', take AoOs on them and an AoO on anyone who charges into your threatened area.