Things I Didn't Expect To Work, But Do

• Self-checkout counters. They're in almost all supermarkets now. I thought their cost + increase in shoplifting + reluctance of people to bag their own shopping would curb their popularity.
• I didn't expect automatic taps would save water, but apparently they do.
• Did you know they can remove the "ball" part of the hip joint for cats and other 4-legged animals and the animal can still function almost normally?