I've always been a fan of harpoons, but never got around to making a full build around them.
In addition to the aforementioned Kuo-Toa and Frostburn/Stormwrack versions, there is the Arctic Harpoon from Races of Faerun which is functionally the same as the FB/SW harpoon (exotic ranged weapon, does damage equal to initial damage if removed) except the heal check to remove it harmlessly takes 1 minute and is DC 10+Damage Dealt, rather than a flat 15. Unfortunately it does 1d8 damage instead of 1d10 and has a range increment of 20' rather than 30', but it has the advantage of forcing them to take the damage twice if they want to remove their move speed debuff in any reasonable amount of time.
A Master Thrower (CW) can pick up a few thrown weapon tricks for harpoons, most notably Deadeye Shot, Doubletoss and Two With One Blow (which could get rather silly as you impale two creatures with one harpoon), and gets the harpoons to 19-20/x3 crit in 5 levels (of course, you can always try to get your hands on
Kaorti harpoons for a x4 crit, but that's a different ball of cheese). As was already mentioned, Brutal Throw and Power Throw or Hulking Hurler if you are large or larger are good options, though since you are already going for BsB those are less important.
Bloodstorm Blade and Thunderous Throw opens a whole can of shenanigans, one of the most notable is the 'BsB Ghetto Charge.' Since Thunderous Throw allows you to treat ranged attacks as melee attacks, and charge requires you to attack from the nearest square you can launch a melee attack (not the nearest adjacent square), when a BsB charges a foe they can actually just run 10 feet and then lob harpoons from 150' away (300' with far shot). Throw in a hop-skip-jump as well as some classic ubercharger junk (Leap Attack(CAdv), Battle Jump(UnEa), Shock-Trooper(CW), & Pounce(
Any number of places) and you can do the whole glass cannon thing from a safe(ish) distance away. Leaping Dragon Stance would help you hit the required "dropping from a height of at least 5 feet above your opponent" for Battle Jump, but any optimized jump check will usually be good enough. Also, if you can't get Pounce, Hurling Charge will let you get at least one extra attack at the end of a BsB Ghetto Charge. But yeah, it kinda of sucks that most strikes can't be used while charging, with the notable exceptions of Battle Leader, War Leader, War Master, and Pouncing Charge.
PS. FB/SW and Arctic Harpoons do damage
equal to the initial damage when removed, not one half. Also, depending on how you read it, Fleshgrinding might make the harpoon less painful/easier to remove than normal.
