Years ago (in vanilla) the spiked chain could be used with weapon finesse. Do not know if this is still the case. This was back in 2007 when I first started playing.
I ... respectfully ... disagree. Third Edition's (and 3.5's) entire rationale for not allowing things like Bracers of Armor and Platemail bonuses to stack, or not allowing a Belt of Giant Strength's bonus to stack with a Bull's Strength spell, is that bonuses from the same source (and only bonuses from the same source) cannot stack. Thus you can't stack two enhancement bonuses, or two Armor, Shield, etc. bonuses. The "spirit" of the game, therefore, requires bonuses from dissimilar sources to stack. I don't believe the game actually defines the bonus from either Keen Weapon or Improved Critical, but the first is obviously an Enhancement bonus, and the other, if not a Miscellaneous bonus (which stacks with anything), would be a ... call it a Skill bonus. Therefore, by the "spirit of the game," they SHOULD stack. The reason they don't is that DMs, or players, or the design team for 3.5 just decided high-level HTH characters were getting too many critical hits for their tastes. It was an arbitrary and unfair decision that goes against both the letter and the spirit of their own rationalizations.
I whole-heartedly second this opinion. In my game they DO stack. However, I have a party that currently has over 60 levels divided by 5 charachters (not including their NPC followers, of which there are about 5, also) and there is only ONE Keen weapon in their possesion. A Fighter with a Keen Greataxe. He also has Improved Critical, Cleave, and Great Cleave. It is fun to watch heads roll! (I play Keen weapons like the old "Vorpal" weapons). He also just got this weapon at level 10 in a Dragon's Hoard. The secret is to give out this power grudgingly, and for a great reward. If every 1st level fighter could get Improved Critical and have a Keen Rapier, then, yes, this would be overpowered indeed.
My game too, when I'm running one. I honestly don't see critical hits as all that important an aspect of the game, and if somebody wants to spend a feat and buy, make or in some other way acquire a keen rapier or falchion, he's more than welcome to do so. Kord knows, in 3.x fighters and rogues need all the assistance they can get . . . :roll: My only caution would be that in a "standard" campaign, it's almost impossible to control what the players can get. A wizard with the Keen Weapon spell and Craft Magic Arms & Armor can easily create a keen weapon at fifth level, which means that by eighth, the fighter could easily have a keen, holy, acid burst, sonic burst, flame burst falchion with Improved Critical. At half the cost of commissioning it, if he's good friends with the wizard player. Still, remember what I said earlier: fighters need all the help they can get. In ToEE, I usually don't even bother including one in the party.
"Obviously", eh? Interesting choice of words. This is ToEE after all As it turns out, they DO stack! It looks like all those years everyone assumed they don't, due to the description. But sure enough, Imp Crit + Keen crafted rapier crits from 12 and upwards! This is a bug, caused by applying untyped bonuses in the engine internals. Oops! Hope you enjoyed this Threadomancy, have fun with it while you still can Props to Sagenlicht for finding this one. Edit: oh man, it's even worse than that, you can also cast Keen Edge and it stacks again... jeeze. 2nd Edit: Oh god, as if it wasn't already busted as hell - the Keen Edge spell stacks with itself. And it only took 17 years to find this out!
When I first started playing ToEE I used to stack them and someone said, "it doesn't work" and explained why so I stopped and now I just feel sad.
In 3.0, I think Imp Critical and keen edge stacked, or that was something proposed by Sean K. Reynolds. Oops?