In Leisure Suit Larry in the Land of the Lounge Lizards and its remakes, Larry Laffer acquires a pocket knife from Wino in return for the jug of wine. He needs it in order to cut the ropes that Fawn tied him to the bed with.
The pocket knife is obtained in the same way, but it is no longer required to cut the ropes, since Larry can also chew through them.
Larry will die if he uses the knife on the taxi driver. The driver will take it as a threat and beat him up.