A high-level npc fighter traveled with the party for a long time in my campaign. He was
very effective, and (although he had a tendency to run off half-cocked and get into lots of trouble) he was devastating in combat.
One of the key things to making him a cool npc to run was the use of custom feats. I have a very large selection of custom feats in my game, and he had several of them. I think a bevy of high-level feats is important to making a high-level (nigh-epic) fighter fun. The problem with the feats in the PH is that they are mostly designed for low to mid level characters. More things like the tactical feats, more feat trees, more style feats- all those are good things.
One example from my campaign of a new feat tree is the Improved Charge tree.
--Improved Charge: get extra +1 to hit when charging.
----Masterful Charge: charge thrice your speed, increase threat range by one while charging.
------Supreme Charge: take an attack of opportunity against one enemy along the line of your charge.
--------Piercing Charge: if you kill your target on a charge attack, keep going and charge a foe behind him.
----------Break the Line: when you charge you force enemies adjacent to your target to back up.
As to 'feat tracks' to build certain types of fighters, I'll get back to you.
