Where did I see the feat...

[Stormborn]

that lets you treat a longsword as "light" for the purposes of two weapon fighting? I think it was in a WotC or Paizo product and I am pretty sure I didnt imagine it. Pretty sure.

 

[diaglo]

monkey grip?

that was in sword and fist iirc.

 

[Old Gumphrey]

Oversized Two-Weapon Fighting, pg. 111 in Complete Adventurer is the only thing close I can think of. Lets you swing a one-hander in your off hand as if it were light.

 

[kenobi65]

monkey grip?

that was in sword and fist iirc.

The 3.5 update for Monkey Grip (now in Complete Warrior) works differently, due to the change in weapon size rules for 3.5.

3.5 Monkey Grip lets you use a weapon that's one size category bigger than you are (e.g., a Large-sized weapon for a human) as though it's the correct size category for you, though at a -2 penalty to attack rolls. So, it'd let you wield a Large shortsword (which, in 3.5, is not the same as a Medium longsword) in your off-hand as a light weapon.

 

[Ambrus]

So, it'd let you wield a Large short sword (which, in 3.5, is not the same as a Medium longsword) in your off-hand as a light weapon.

Unless one is using the Weapon Equivalencies option rule from the DMG (page 27), which seems to be a fairly common practice in my experience.

 

[Stormborn]

Oversized Two-Weapon Fighting, pg. 111 in Complete Adventurer is the only thing close I can think of. Lets you swing a one-hander in your off hand as if it were light.

We have a winner! I must have associated it with the LS because of the character I was thinking off. Thanks Gumphrey!