Here are some great "What if?" questions from Roger von Oech:
What if animals became more intelligent than people?
What if we had mouths in the palms of our hands?
What if men also had babies?
What if we had edible clothing?
What if we elected our officials by lottery?
What if human life expectancy were 150 years?
What if people exuded a foul smell from every pore whenever they did anything bad?
What if people had wheels for feet?
What if you had no memory whatsoever of your first ten years?
What if people had pliers for hands?
What if human bones were made of glass?
What if there were no trees?
What if you could only talk one hour a day?
What if gravity were half as strong?
What if people ate only one meal every two days?
What if people exuded a terrible smell from all their pores whenever they behaved unethically?
What if all human beings died at the age of 50?
What if your sense of smell were amplified by a factor of 100?
What if trees developed the ability to move themselves up to 2 meters a day?
What if all right angles (90 degrees) were prohibited in all new construction?
What if every person was required to spend at least two years outside of the country where they were born?
I have created some systematic techniques to create "What if?" questions so that their creation is less dependent on huge "creative leaps":
Creating "What if?" questions: conversion by degree
Creating "What if?" questions: total conversion
Creating "What if?" questions: sentence restructuring
Creating "What if?" questions: the trigger
creativity ideas idea generation what if