The only time I ever forgot to put the gear down was when my then 22 mo old "have to go pottie" approaching the DFW metroplex. Charts were buried back in the Mooney's rear compartment, except for DFWs.
The controller gave me a heading, told me he'd let me know which of the FOUR runways it'd be, asked for 170 knots. When I was cleared, it was for 17L, with a 747 in trail.
170 knots it was, out we popped at ~250 agl, but I couldn't get it slowed down. Nose up, big slip, 3000 feet down the runway, finally realized the big silver gear handle wasn't there (Turbo M20F), put 'em out, touched in the last 3000 feet, taxied off the second to the last high speed taxiway, and was THANKED by the controller.
I was covered with sweat.