The ornamental design for an extinguisher, as shown and described.
1. Extinguisher
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 : Top
1.7 : Bottom
The broken lines show portions of the extinguisher that form no part of the claimed design. Materials used to manufacture the product include synthetic resin and metal.