sensible F
in 25 years of flying and thousands of hours in retractable twins I have never landed gear up!
I was very close to doing so once (see previous post of mine in this thread)
Correct use of checklists will reduce the majority but I firmly believe the bells and whistles fitted to most aircraft (some up to 30 years old plus ) are inadequate.
Pilots are often not alerted by bells and whistles but are alerted by electronic voice commands! Gear Gear Gear! is something no pilot would confuse and fitted to modern aircraft.
It is when a pilot least expects it that the Gear can be missed! Under extreme concentration or poor checks
Pace