Though I remain among "those who will," I have scared myself. Once, I was flying a practice nonprecision approach to my home airport. It was VFR, but weather was moving in. I was also listening on the advisory frequency for a fellow pilot who I knew was inbound behind me, both of us having left from the same airport. I was concerned that he might get caught in the advancing storm (lame excuse No. 1). The recommended method for descending to MDA on a non-P approach in a Bonanza is to lower the gear -- which I did on passing the final approach fix 4.2 miles from the airport. Then, when I entered the pattern, I must have flipped the old-style 'piano key' switch at the spot in the pattern where I usually lower the gear. It doesn't help that the early Bonanza piano key gear switch looks pretty much like all the other switches in the row. When the gear is down, the switch lines up flush with all the others that are not activated. When the gear is retracted, the switch sticks up separate from all the others in 'activated' posture. I clearly remember that in my distracted mind, I felt I was 'activating' the gear by flipping the switch to its 'up' position (even lamer excuse No. 2). My first GUMP check caught the miscue as I turned base -- about the same time the horn sounded and a friend, who was waiting to take off, transmitted, "Uhhh, Mark??" before he saw the wheels coming down.