We present DexController, which is a hand-held controller leveraging grasp as an additional modality for virtual reality (VR) game. The pressure-sensitive surface of DexController was designed to recognize two different grasp poses (i.e. precision grip and power grip) and detect grasp force. Based on the results of two feasibility tests, a VR defense game was designed in which players could attack each enemy using the proper weapon with a proper level of force. A within-subject comparative study is conducted with a button-based controller which has the same physical form of DexController. The results indicated that DexController enhanced the perceived naturalness of the controller and game enjoyment, with having acceptable physical demand. This study clarifies the empirical effect of utilizing grasp recognition on VR game controller to enhance interactivity. Also, we provide insight for the integration of VR game elements with the grasping modality of a controller.