Shotput is an elegantly simple sport: throw the sphere as far as possible.
Consider lifting restrictions to make the sport simpler: the thrower does not need to stay inside the throwing circle but need only stay behind a line. The thrower may use a running start. This would make it a little like bowling. Somewhat more complicated is to have a pool of water or sand pit in front of the line: the thrower is permitted to fall in the water or sand after throwing, so can be running at maximum speed at the point of release right at the line. How would throwing technique change?
Apply similar anarchy to javelin: instead of a sphere, throwers are permitted to choose any shape of at least the specified weight. If technology improves so that throwers are throwing too far (as has already occurred once in javelin), increase the minimum weight. We probably need rules to forbid, for example, powered flight. I suspect the best shape might resemble an Aerobee.
There will be a frontier of records of weight versus distance.