Look no further than your Players Handbook:
Combat Expertise, Improved Trip (Flail)
Dodge, Mobility, Spring Attack
Power Attack, Cleave, Improved Bullrush
Weapon Focus, Weapon Specialization
Iron Will, Lightning Reflexes
Combat Reflexes
Improved Initiative
The intent of a Weapon and Shield Fighter is two-fold: Do not get hit often. Protect the weaker party members.
It is NOT to wipe out enemies with the fewest number of swings of a weapon like a Two Handed Weapon fighter.
It is NOT to look flashy like a Two Weapon fighter (which is mostly what they do, they do not typically do that much more damage than a Weapon and Shield Fighter).
So, in order to outlast opponents, the Weapon and Shield Fighter needs a great Defense and good saving throws. Defense over Offense.
Yes, a Two Handed Weapon fighter will do more damage per successful attack. However, that does not mean that they will necessarily kill their opponent that much faster. They may, they may not.
If your Two Handed Weapon fighter is doing an averge of 25 points of damage and your Weapon and Shield fighter is doing an average of 18 points of damage, and the opponent has 52 hit points, both of these fighters will take him out in about 3 successful hits.
Two Handed Weapon fighters often "waste" a lot of damage on the last hit that takes out an opponent. If the opponent has 10 hit points or less, you do not need to do 30 or 40 points of damage to him to take him out. Even when they do take out an opponent in fewer successful hits, it is typically one fewer hit, not many fewer hits.
Damage Reduction plays a part in this as well, but eventually most PCs get around most Damage Reduction with spells or special weapons.
There are also some other factors that are important here. If your Weapon and Shield fighter rarely gets hit, the party healer (be it a Cleric or whatever) rarely has to heal him in combat. This typically gives the party healer one or more rounds every few combats in which to do other useful actions and also slightly decreases the number of spells he needs to cast on healing.
Also, have your Weapon and Shield Fighter use a Tower Shield. It is the most under-utilized item in many games. At high level, the other two fighter types have (without other items or Dodge bonuses) at most AC 26 or so from (+5 Mithral Full Plate) Armor and Dex (and yes, they could have an Animated Shield, but that is the first obvious item that opponents should try to Sunder or Dispel IMO).
The high level Weapon and Shield Fighter can have AC 35 from (+5 Mithral Full Plate) Armor and (+5 Tower) Shield and Dex without Dodge bonuses or anything else. That takes out 35 of the opponents attack without a single other item or feat. A few other AC items, 5 out of Combat Expertise, and 1 for Dodge puts him at AC 45+. Even 20th opponents will only hit AC 45+ maybe 30-50% of the time or so with their first attack compared with the 95% of the time or so with their first attack and 75%-95% on the second attack against the AC 31+ of a Two Handed Weapon or Two Weapon Fighter (assuming they do not do full combat expertise). Do the math. 30% on the first attack, 5% on the other 3 attacks = 45% damage on average versus 95% + 75% + 50% + 25% = 245% or about 5.5 times as much damage received per full round attack opponent (and 2 times as much damage received on single attacks). Even with a high to hit opponent at that level, it is still in the range of 50% + 25% + 5 % + 5 % = 85% versus 95% + 95% + 70% + 45% = 305% or 3.5 times as much received damage.
This is especially useful when outnumbered. Two Handed Weapon and Two Weapon Fighters can fall in a single round if outnumbered two to one or more. Or it can be worse in the long run when monsters have special attacks such as poison or energy drain.
Finally, consider having your Weapon and Shield Fighter take two levels in Ranger (Rapid Shot for when opponents are at range and Tracking) and two levels of Cleric. This gives him +4 to Fort saves and +2 to Reflex and Will saves most levels, more skills (including Spot and Listen as class skills for those levels), minor healing and other minor spells (like Protection From Evil), for the cost of 1 BAB, 4 hit points on average, and two Fighter feats that are not as critical due to how many feats he already will have.
Personally, I think Weapon and Shield Fighters are the most powerful fighters in the game because if built well, they have the best survival chances (for Fighter types). They can get even better with some feats not in the PHB (like Improved Combat Expertise).
There are plenty of PCs in most groups who can dish out damage, but not all PCs in the game can still be standing most combats after many rounds of combat.
