Using just the core rulebook and the advanced player's guide, what would be an optimal build for a fighter using 25 points for point-buy character generation? Assume it's a level 10 fighter intended to focus on dealing high damage to single targets consistently each round.
In general, two-handing with Power Attack is the best start to DPS. Now with the APG there's the "Two-Handed Fighter" fighter variant that helps it even more.
At level 10, you should be able to easily have a 22 STR (start with 18 +2 racial +2 levels) plus magical strength enhancement of +4. Of course you have to dump a bunch of other stuff but you want DPS so here's the DPS. 26 STR (+8).
If you're human, you have 6 normal feats and 6 fighter bonus feats
Your BAB is +10/+5. Power attack gives you a -3/+9 to hit/damage. Weapon training gets you +2/+2. Weapon focus and weapon specialization get you +1/+2. So when power attacking, which generally you should, you're at +18/+13 to hit and +21 damage.
Now you have two scenarios - standard action and full attack.
Standard action - with overhand chop (2wf variant) you get double STR bonus to damage on the attack. Vital strike gets you double base damage. Assuming you're using a greatsword, that's 4d6+29 damage.
Full attack - backswing (2wf variant) gets you double STR bonus to damage on the second attack. Then you take Furious Focus (APG feat) so the PA penalty doesn't apply to your first attack. Now you're at +21(2d6+21)/+13(2d6+29).
Toss in Improved Critical, Critical Focus, Cleave, and Great Cleave. And then, you know, 6 other feats you want. That's without getting fancy with tricks, I don't like it to be too cheesy, but there with some solid basics you're tossing in a good average damage. Of course any rounds that you benefit from buffs, Enlarge, etc. is a good addition.
Here, I Hero Labbed up a level 10 two weapon guy and spent his money on an optimal damage (not really AC or anything else) loadout. I did give him step up, disruptive, and spellbreaker because if you are focusing on single opponent combat the BBEG is likely to be a caster a lot of the time.
TWO HANDER GUY CR 9
Also, having a weapon with reach (like a Lucerne Hammer, which does D12 base damage) gives you the ability to hit enemies 10 feet away, and an attack of opportunity on anyone who moves up to be able to attack you (unless they just move 5').
So having a reach weapon gives you many more opportunities for attacks of opportunity and also for cleaves/great cleaves etc...
This, combined with the fact that its a two handed weapon, means you could take all of the feats described by the person above, and also invest in some Dexterity and combat reflexes, and maybe the cleaving finish feat, or Lunging (which can give you a +5ft reach, so a 15 foot reach in total - thanks to the poster below for correcting me on this).
The one problem with 2 handed weapons and power attacks and lunging is that these can lower your AC (no shield, -2AC penalty for power attacks, and -2AC penalty for lunging). So you need plenty good armour and HP to make up for this.