Asides from the more general combat maneuvers (tripping, disarming, sundering etc.) most ability feats are going to be hindered by specificity: if you want the option to do something cool with your weapon, chances are it's going to have to be a specific kind of weapon. Want Boomerang Daze? Well, you'd best be using a crapsack boomerang or it's not happening. Think of it as the divine/arcane split, except much more unfair and crippling. We're not here to complain, though, we're here to break the system open a little and make it work for us. This game is about open-ended character creation, and one should be able to fit together options however they please. So wouldn't it be nice to make use of all those neat weapon-specific feats on whatever you like?
Yet again, thank goodness for the Tome of Battle, that latter-day bastion of hope for giving Good Things™ to melee. Buried towards the end of the book, among mostly filler and weapons of legacy nonsense, lays the gem that is the aptitude weapon special quality. Not to be confused with the warblade's class feature, Weapon Aptitude, troublingly from the same book, an aptitude weapon has the following benefit:
|The aptitude property lets a wielder apply his expertise with another type of weapon to the aptitude weapon. Thus, the master of a greatsword is the also the master of any aptitude weapon.
Aptitude weapons have no special appearance.
Anyone can wield an aptitude weapon, but to gain any benefit from it, a wielder must have feats that are tied to the use of a particular weapon type.
Activation: An aptitude weapon's magic is worthless in the hands of someone who lacks the appropriate feats, but anyone with the right feats gains the benefit by just wielding it.
Effect: A wielder who has feats that affect the use of a particular type of weapon, such as Weapon Focus, Greater Weapon Focus, Weapon Specialization, or the like, can apply the benefits of those feats to any weapon that has the aptitude quality. In addition, if any of the wielder's weapons use feats are specifically keyed to the aptitude weapon's type he gains a +1 bonus on attack and damage rolls.
Aura: Faint evocation.
Requirements: Craft Magic Arms and Armor, Weapon Focus (weapon being enchanted).
Price: +1 bonus
So essentially, you can let any feat that's specific to one or more weapons apply to an aptitude weapon, even if it's of a non-compatible type. I can picture the designers' intent being fairly modest: a character has Weapon Focus (longbow), and then they pick up a +1 aptitude greatsword, letting them reap the world-shaking benefits of Weapon Focus a second time at no further cost. The thing is, the most powerful weapon-specific feats aren't the ones that let you pick what they apply to. After all, if you're the one picking them, you're probably going to be choosing them for the weapon you're using. If you've got Weapon Focus (battleaxe), Weapon Specialization (javelin) and Improved Critical (gnome hooked hammer), you don't need an aptitude weapon, what you need is a new character.
So you know well enough to apply your feats to whatever form of pointed stick you happen to be holding in your grubby mitts. Which feats to pick, though? Fortunately I have compiled a short list for you blebs, featuring the feats designed to apply to only one specific weapon. Since they have a higher price than most feats (having to take the feat and its prerequisites and then use a substandard weapon, and in the case of exotic weapons, having to take the proficiency feat on top of that,) said feats are usually marginally stronger than most ho-hum combat feats. Do note that I only included the options that are either good or at least interesting. Yes, Turtle Dart applies, but you're still not going to take it.
- Axespike (Races of Stone): When you make a full attack with an aptitude weapon, you may make an additional attack with your armor spikes, but with a -5 penalty and only half your Str bonus to damage. Kind of like a natural secondary weapon.
- Boomerang Daze (Races of Eberron): Anyone you hit must make a Fortitude save (DC 10 + damage dealt) or be dazed for one round. Being dazed is extremely powerful, one of the best conditions to inflict in the game, and virtually nothing is immune to it - this is a huge deal. The boomerang is a lousy weapon, but it's worth consideration thanks to this feat. Using Boomerang Daze in conjunction with an aptitude weapon with a larger damage die is downright dangerous. This is entirely worth building an entire character around.
- Boomerang Ricochet (Races of Eberron): If you strike a foe, you may immediately make a second attack roll against an adjacent target with a -2 penalty. Since you're using a boomerang, both foes are naturally subject to Boomerang Daze. Again, much more impressive with a reach weapon and iterative attacks.
- Eagle's Fury (Sandstorm): With a full attack, you get one extra attack at your highest base attack bonus, but each attack in the round takes a -2 penalty. Flurry of Blows for weapons, essentially. Stacks with Two-Weapon Fighting!
- Hammer's Edge (Complete Warrior): If you hit your opponent with two aptitude weapons in one round, they must make a Fortitude save or fall prone. Real rules lawyers might be able to convince the DM that this works for every hit with an aptitude weapon, since every aptitude weapon both counts as a "sword" and a "hammer." The fact you need to take Weapon Focus twice is completely wasted, though.
- Improved Weapon Familiarity
- Improved Unarmed Strike: You can freely choose to deal lethal or nonlethal damage with an aptitude weapon. This results in a lousy and expensive merciful weapon, but IUS is a prerequisite for more intriguing feats, like Roundabout Kick and Snap Kick.
- Lightning Mace (Complete Warrior): Whenever you threaten a critical with an aptitude weapon in each hand, you get an additional attack at the same bonus. Works much better with a light weapon that has a large threat range (say, a +1 keen aptitude kukri for 15-20.) Add in the Blood in the Water stance, make full attacks and go to town.
- Hand Crossbow Focus (Drow of the Underdark): You can reload your weapon as a free action and you get Weapon Focus thrown in for free. Makes the heavier crossbows more attractive... and a ballista downright gorgeous.
- High Sword, Low Axe (Complete Warrior): If you hit your opponent with two aptitude weapons in one round, you get a free trip attempt. Very similar to Hammer's Edge, but it's easier to improve your tripping capabilities than it is to lower a foe's Fortitude save
- Roundabout Kick (Complete Warrior): If you score a critical hit, you immediately get an extra attack at the same bonus. Could be a little ridiculous if you stack it with Lightning Mace.
- Sanctify Martial Strike (Book of Exalted Deeds): Your aptitude weapons deal 1 more damage to evil foes, or 1d4 more to evil outsiders and evil undead. Plus, it's good-aligned for overcoming damage reduction.
- Shield Charge (Complete Warrior): If you charge a foe, you get a free trip attempt without provoking an attack of opportunity or risking being tripped in return. Good luck making use of Improved Shield Bash, though.
- Spellrazor (Races of Stone): As a full-round action, you can cast a touch spell, attack with it, then attack with an aptitude weapon. Nice on a gish, and especially if combined with a spell storing weapon.
- Spinning Halberd (Complete Warrior): Make a full attack with an aptitude weapon and you get a +1 dodge bonus to AC and a free attack with a -5 penalty that deals 1d6+½ Str bludgeoning damage. Pairs nicely with Combat Rhythm or spiked chain builds.
- Stunning Fist: You can use an aptitude weapon to make a stun attempt. Since it still uses your Wis modifier for the DC, it might have potential on a Zen Archery cleric with an aptitude bow. Also is a prerequisite for many feats, including some intriguing standouts like Freezing the Lifeblood and Unbalancing Strike.
- Sugliin Mastery (Frostburn): You can attack with an aptitude weapon as a standard action, or full attack with one as a full-round action. Sounds redundant, right? What about with an aptitude ballista?
- Three Mountains Style (Complete Warrior): If you strike a foe twice in the same round, it must make a Fortitude save or be nauseated for one round. The prerequisites are sure harsh, though.
- Versatile Combatant (Drow of the Underdark): You don't provoke attacks of opportunity for making ranged attacks with aptitude weapons, and it gives you Two-weapon Fighting for free.
- Weapon Supremacy (Player's Handbook II): This feels like a real flavour fail, but by all means, the samurai who dedicated his life to the mastery of the katana should be able to dabble in mastery of the caber on the side.
So it turns out there are a lot more feats to use with your favourite weapon than you thought. Of course, as was hinted a couple times there, if your favourite weapon is a ballista, then a whole world of possibilities opens up. Ballistae basically work as any normal weapon, requiring an attack roll and being aimed at a creature. Unlike most weapons, though, they deal 5d8 damage.
Thus, a +1 aptitude heavy ballista being wielded by a user with Hand Crossbow Focus and Sugliin Mastery can be used to make full attacks. While it might be unwieldy for a traditional character to be making use of a ballista, transporting it with tenser's floating disk or even just a wagon should do the trick. Add Boomerang Daze and Penetrating Shot to the mix and you could have one heck of a medieval tank gunner. Just watch out for dungeons with five foot wide corridors.