Best weapon enchantment For a character thats gets lots AOO

[Nosta]

so I am using A fighter level 12
and I was curious as to what weapon ability could be put on a reach weapon that would benefit a fighter that gets a lot of AOO

[Khedrac]

well, that depends what you want it to do.

Extra Damage would be something like acidic.
Wounding could be a good way to annoy attackers as you get to weaken them before they hit you.
Vorpal though usually not worth the +5 may give you more return simply from the number of attacks you make.
Vicious is more extra damage but you better be able to heal yourself.

[Amphetryon]

For extra damage, I generally prefer Collision and/or Vicious. For an AoO build, I might try to work with the DM to create an enhancement that either stopped movement, or pushed the target back 5', if the Character was not natively able to do either of those tricks.

[Necroticplague]

Depends. What weapon is this going on? Is it the same one as most of the AoOs are being taken with? Or is it for the armor spikes/razors? Usually, can't go to wrong with loading up armor spikes with "while weilding....." properties, like Eager.

[OldTrees1]

You probably are already doing enough damage so here are some non damage abilities that synergize with your number of attacks.

+1 abilities
Cursespewing: On hit, Will Save DC 14 or -4 to everything (http://www.realmshelps.net/magic/weapon/Cursespewing)
Diseased: On hit, Fort Save DC 12 or 1d3 Dex and 1d3 Con from Filth Fever (http://www.realmshelps.net/magic/weapon/Diseased)
Exhausting: On hit, Fort Save DC 14 or fatigued (does not escalate) (http://www.realmshelps.net/magic/weapon/Exhausting)
Silent Strike: On hit, Will Save DC 15 or be silenced (http://www.realmshelps.net/magic/weapon/Silent_Strike)
Smoking: 5ft square of nauseating(Fort DC 14?) fumes that provide one half concealment (http://www.realmshelps.net/magic/weapon/Smoking)
Sure Striking: Bypass DR/alignment (http://www.realmshelps.net/magic/weapon/Sure_Striking)

+2 abilities
Metalline: Change the metal material of the weapon (http://www.realmshelps.net/magic/weapon/Metalline)
Strength Sapping: On hit, Fort Save DC 15 or exhausted (http://www.realmshelps.net/magic/weapon/Strength_Sapping)
Subjugating: On hit, Will Save DC 20 or become Shaken (or Frightened if already shaken but does not self stack) (http://www.realmshelps.net/magic/weapon/Subjugating)
Vampiric: On Hit Fort Save DC 16 or drain 1d4 hp (drained hp becomes temporary hp if wielder is already full hp) (http://www.realmshelps.net/magic/weapon/Vampiric)
Wounding: On hit, 1 Con damage

+3 abilities
Clouting: On hit Fort DC or be knocked back 10ft and Fort Save DC 19 or be stunned 1 round (http://www.realmshelps.net/magic/weapon/Clouting)
Marrow Crushing: On hit deal 1 Con damage (http://www.realmshelps.net/magic/weapon/Marrowcrushing)
Weakening: On hit deal 1 Str damage (http://www.realmshelps.net/magic/weapon/Weakening)

[Jack_Simth]

Vampiric: On Hit Fort Save DC 16 or drain 1d4 hp (drained hp becomes temporary hp if wielder is already full hp)Note that the version found in the MIC is mostly better - it's a d6.

[MilleniaAntares]

On my cell phone, but there is a special ability that gives you an iterative for one AoO per round.

[Troacctid]

Paralyzing, from Book of Exalted Deeds, is pretty good.

Why did you make two threads for the same question? What was wrong with the first one?

[Snowbluff]

You probably are already doing enough damage so here are some non damage abilities that synergize with your number of attacks.

+1 abilities
Cursespewing: On hit, Will Save DC 14 or -4 to everything (http://www.realmshelps.net/magic/weapon/Cursespewing)
Diseased: On hit, Fort Save DC 12 or 1d3 Dex and 1d3 Con from Filth Fever (http://www.realmshelps.net/magic/weapon/Diseased)
Exhausting: On hit, Fort Save DC 14 or fatigued (does not escalate) (http://www.realmshelps.net/magic/weapon/Exhausting)
Silent Strike: On hit, Will Save DC 15 or be silenced (http://www.realmshelps.net/magic/weapon/Silent_Strike)
Smoking: 5ft square of nauseating(Fort DC 14?) fumes that provide one half concealment (http://www.realmshelps.net/magic/weapon/Smoking)
Sure Striking: Bypass DR/alignment (http://www.realmshelps.net/magic/weapon/Sure_Striking)

+2 abilities
Metalline: Change the metal material of the weapon (http://www.realmshelps.net/magic/weapon/Metalline)
Strength Sapping: On hit, Fort Save DC 15 or exhausted (http://www.realmshelps.net/magic/weapon/Strength_Sapping)
Subjugating: On hit, Will Save DC 20 or become Shaken (or Frightened if already shaken but does not self stack) (http://www.realmshelps.net/magic/weapon/Subjugating)
Vampiric: On Hit Fort Save DC 16 or drain 1d4 hp (drained hp becomes temporary hp if wielder is already full hp) (http://www.realmshelps.net/magic/weapon/Vampiric)

+3 abilities
Clouting: On hit Fort DC or be knocked back 10ft and Fort Save DC 19 or be stunned 1 round (http://www.realmshelps.net/magic/weapon/Clouting)
Marrow Crushing: On hit deal 1 Con damage (http://www.realmshelps.net/magic/weapon/Marrowcrushing)
Weakening: On hit deal 1 Str damage (http://www.realmshelps.net/magic/weapon/Weakening)

Doesn't basic wounding do 2 con damage for a +2?

[Thurbane]

Make it from Gehennan Morghuth Iron? The save is pathetically low, but if you hit people often enough, everyone rolls a 1 sooner or later...

[OldTrees1]

Doesn't basic wounding do 2 con damage for a +2?

Yes, although only 1 Con damage. The site I am linking to is only 95% accurate so I forgot about Wounding being better (wounding on realmshelp is listed as 1hp/round).