Grippers have been shown using jamming of granular media grasp a large range of objects by pushing against them (with an activation force) to conform the gripper to the object's shape before grasping them with the intent to make universal grippers. This paper presents two effective modifications to jamming gripper designs (adding small nubs and fluidizing the granular media) resulting in significantly larger holding forces (typically 60%) and increasing the range of object geometries. The paper presents the design and fabrication of these devices and explores the range of objects and conditions empirically. Experiments also show that the nubs enable the grasping of smaller objects in which the gripper can engage interlocking forces in the granular media.