Well, there's not much point in suggesting prestige classes if you've already ruled out using them.
So, a 19th level drow fighter type.
One option is Ftr 19. You get 17 feats to play with. Have fun.
Another option would be Ftr 16/Rgr 1/Bbn 2. You lose 1 feat and 1 point of will save but gain the first level of Uncanny Dodge, rage, and favored enemy, some good skill points, and three point of fort save and 1 point of reflex save.
Another option would be Ftr 12/Bbn 5/Rgr 2. That buys you Improved Uncanny Dodge, 2 rages/day, and the first fighting style option for ranger.
But, since you said you didn't want to do two weapon fighting and you probably won't be using a bow much, you might drop ranger in favor of monk. (Who knows how or when he trained as a monk, but he must have):
Ftr 12/Bbn 5/Ex-Monk 2
Of course, all of these cause favored class problems, but he's an NPC so he doesn't need to worry about xp penalties.
As for feats--well, you need to decide how he's going to fight. Since he's got 21st level equipment, he'll have an animated shield so you can forget sword and board. Since you don't want TWF, that leaves a two handed fighting style. Since you don't want exotic weapon master, there's no point in using a bastard sword instead of a greatsword. So, give him a greatsword. Unless, of course, the PCs don't all have heavy fort armor, in which case, give him a falchion. (By 19th level, his damage bonuses should be high enough that improved crit range gives him more damage than the larger dice).
Feats: Combat Reflexes, Imp Crit, WF, GWF, WS, GWS, Power Attack, Cleave, Close Quarters Fighting, Dodge, Mobility, Elusive Target (an excellent feat for an NPC who will be outnumbered by PCs), Improved Bull Rush, Shock Trooper. (And make sure to give him ledges and things to bull rush PCs off of). If you have more feats to play with, you might want to go for Combat Expertise and Improved Trip then and Improved Sunder and Combat Brute. Give him Leap Attack to really crank the damage.
