Neb's Nasty Cutter

Neb's Nasty Cutter is an enchanted dagger +2 which can poison enemies when they are hit. The target must make a save vs. poison or suffer 2 points of damage every seconds until 10 seconds have passed. This weapon can only do this 10. After that, the weapon is simply a Dagger +2. This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition. This dagger is dropped by Neb in the derelict house in Athkatla Bridge discrict during Gain the Services of Sir Sarles for the Temple.

In-game description
"This is a vicious weapon used by Neb, covered with old blood and coated in a poison that is both quick-acting and extremely deadly. Only the truly evil would dare to use this item on their own. Once the poison is used up, however, Neb's Cutter will act as a normal enchanted dagger."