I almost forgot.
Proviso, I think people should include whatever works into their games - if swords that do 300D6 or magic missiles with death effects are the right thing then I think thats great.
However:
Pet Hate Rant
I heartily dislike a lot of the 3rd party weapons (and some of the stuff from Sword and Fist). The players guide weapons follow a simple system... don't understand why other stuff can't stick to it or at least reasonably close to it. Relics and Rituals cleaver is a prime example of a badly designed weapon, imo.
Basically as you go from simple>martial>exotic, you get an improvement for each level.
An improvement is an increase in damage, an increase in crit range OR multiplier or a special ability.
eg
medium weapons
heavy mace > Longsword > bastard sword
D8 20 *2 > D8 19-20*2 > D10 19-20 *2
OR
heavy mace > light flail
D8 20 *2 > D8 20 *2 + better trip
OR
heavy mace > warhammer
D8 20 *2 > D8 20 *3
OR
Longsword > Double sword
D8 19-20 *2 > D8 19-20 *2 + special (off hand is considered light).
Or you can muck about with these within a level
Longsword = Scimitar
D8 19-20 *2 = D6 18-20 *2
Increasing in size scales up the damage:
Shortsword > Longsword > Greatsword
D6 > D8 > 2D6
Hand Axe > Battle Axe > Greataxe
D6 > D8 > D12
Etc.
Nearly all the weapons there can be derived using this with a little bit of flexing to it: A couple of weapons do blur this a little, for example Mighty bows are pushing towards exotic weapons, imo. The finessable ability of rapiers is a borderline case...
In the case of the above big doublesword, if I had to allow it, I'd make it take 5 exotic feats to use as a normal double weapon.
1 = double sword
2 = main damage > D10
3 = main damage > 2D6
4 = off hand damage > D10
5 = off hand damage > 2D6
with a standard -4 nonproficiency penalty for each feat lacking.
/Pet Hate Rant
Edit: Formatting+sense