[Weapon] It's the ropes and the reins and the joy and the pain...

[The Vorpal Tribble]

I dunno if it's been done before, but here is my go at it...

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Lasso


A lasso is used to ensnare enemies. When you throw a lasso, you make a ranged touch attack against your target, which must be within two size categories of you. A lasso’s maximum range is 10 feet. A lassoed creature moves at only half speed and cannot charge or run. If you control the trailing rope by succeeding on an opposed Strength check while holding it, the lassoed creature can move only within the limits that the rope allows (the trailing rope is up to 60 feet long). You can tie the lasso to another willing being or object (such as the pommel of a saddled horse) with a DC 10 Use Rope check. You may then combine your modifier with that of the willing being. If the lassoed creature attempts to cast a spell, it must succeed on a DC 15 Concentration check or lose the spell.

You can make trip attacks with a lasso. If you are tripped during your own trip attempt, you can drop the whip to avoid being tripped.

When using a lasso, you get a +2 bonus on opposed attack rolls made to disarm an opponent (including the roll to keep from being disarmed if the attack fails).

Ranged Exotic Weapon

Cost  DMG (S)  DMG (M)  Critical  Range Increment  Weight  Type
1 gp  -        -        -         10 ft.           2 lbs.  -

[arguskos]

It has been done before, in Races of Faerun.

The relevant bits from that lasso version are as follows:
-Against a medium or smaller creature, you make a ranged touch attack. If you succeed, make a grapple check at a -4.
-You can't pin or damage them with the lasso.
-If you grapple them, you can trip them with the lasso.
-You aren't considered grappled when you grapple with the lasso.

Pretty much, it's an uglier version of your lasso, but it allows grapples and trips, while yours only permits slowed movements and trips. Not sure which is more useful really, but I thought you should know about it.

-argus