Help on optimizing a guisarme wielding tripper?

[Critical]

Hey, I'm helping my friend on making a fighter contributing, and I decided it'd be nice to make a tripper. So far we're level 4, and he's a straight fighter, with those feats: Combat Reflexes, Combat Expertise, Improved Trip, Power Attack, Deft Opportunist, Knock-Down. Any pointers on what feats to take and in what direction to move? Please, no spiked chain, because it doesn't add to the flavor, and no setting-specific material.

[Ernir]

It might be a good idea to move away from pure Fighter-trippiness, sounds like you have it more or less covered already.
If you want more AoO-ness, how about Karmic Strike and later on Robilar's Gambit?

EDIT: Are the levels at 4+ married to Fighter, or is suggesting Warblade from now on OK?

[gallagher]

It might be a good idea to move away from pure Fighter-trippiness, sounds like you have it more or less covered already.
If you want more AoO-ness, how about Karmic Strike and later on Robilar's Gambit?

EDIT: Are the levels at 4+ married to Fighter, or is suggesting Warblade from now on OK?

and a level of SLT Barb

[PId6]

and a level of SLT Barb

Alongside a nice Crusader dip at 9th for Thicket of Blades.

[Critical]

Thought about Karmic Strike/Robilar's Gambit, but no reach for adjacent squares makes it kind of sucky. And no, it's not married to a fighter, in fact, the build was made spontaneously, when the session was going, so it was more of a filler one for one session and, I think, could be a bit shuffled up. But it'd be cool to make a straight effective Fighter 20, indeed. Thinking about it more properly and having access to the books, I've came to this: Wolf Totem Barbarian 2/Fighter 4/Horizon Tripper X, with feats as follows(the DM mentioned the possibility of taking Faerun feats, because it exists on some other plane): Jotunbrud, Combat Reflexes, Improved Trip(Barbarian Bonus), Deft Opportunist/Improved Sunder, Power Attack, Knock-Down, Endurance, Combat Brute/Improved Sunder.

Oh, and no ToB.

[Greenish]

Thought about Karmic Strike/Robilar's Gambit, but no reach for adjacent squares makes it kind of sucky.

Armour spikes. Try to get Jotunbrud to qualify for Knockback.