I like Wave Launcher. You can change the location of initiating Wave Launcher to the bottom or left or right side of the screen and more importantly, you can reduce the gesture-area thickness in portrait or landscape in Settings to as little as 1%, reducing interference issues substantially as well as the size of the gesture-area (e.g. along the whole length of the bottom screen area or a small and thin rectangular shaped area near the middle of the bottom screen area or to the left or right side of the bottom screen area). Finally, you can set Wave Launcher to be disabled in landscape orientation.