The tool has a driver blade (14) and a nosepiece (18), and is configured for feeding fasteners (22) to the nosepiece for engagement by the driver blade for driving into a workpiece (28), each fastener (22) defining a plane, further includes a deformation formation (56) in the nosepiece (18) configured for engaging a portion of each of the fasteners so that upon impact of the fastener (22) by the driver blade (14), the engaged fastener portion (38) is deformed in a direction transverse to the plane to define a deformed portion, the deformed portion configured for providing a clamping force upon at least one of the workpiece (28) and a workpiece material (32) being secured to the workpiece. A fastener is provided for use in such a tool and includes a crown (30) configured so that, upon impact with at least one of the workpiece (28) and the workpiece material (32), the crown (30) has a nonlinear configuration.