The following is based on Grand Theft Auto Vcut content and has not been verified by canon sources. Please do not add unverified or speculative content to this article unless confirmed by Rockstar Games or in-game data.
The Lasso is a weapon that was scheduled to be featured in Grand Theft Auto V, but was cut from the final version of the game. An image of it can be found in the game files.
Not much is known about it, although it is believed that it was going to behave similarly to the lasso featured in Red Dead Redemption, another game edited by Rockstar Games. This would include lassoing pedestrians and eventually hogtying them. Considering that GTA V also posseses some RDR's leftovers (i.e. horses), this would be likely.