The original question asked about landmark cars that changed the industry.
c1900 De Dion-Bouton introduced the sliding-pinion gearbox, basis for all later manual transmissions, even today.
The Oldsmobile curved-dash c1904 was the first mass-produced car - and it was reliable.
1904 Mercedes introduced the layout that was to set the pattern for most cars; radiator/engine/gearbox with H change driving through a propellor shaft to the rear axle.
The Ford Model T - high quality materials yet low price showed what could be done to democratise motoring. The flywheel magneto and planetary transmission based upon those of the British Lanchester. Anybody could now change gear silently!
The 1912 Cadillac, first to have electric starting allowed motoring to be enjoyed equally by women.
The 1924 cross-plane V8 Cadillac wholly solved the former V8 vibration problems - leading to that engine form becoming nearly universal for larger cars.
1928 Cadillac introduced syncro-mesh enabling anyone to change gear.
1928, the British Daimler Co introduced the combination of 4-speed pre-selector epicyclic gearbox, fluid coupling and steering column selector, all developed in the 1930s by GM, following their purchace of one example in 1931 at the London Motor Show, into the 4-speed Hydramatic , in its turn the precursor of all automatic transmissions for the next sixty years - and counting.
1949 Cadillac introduce the first high-compression engine, taking advantage of high-octane fuels, giving simultaneously more power and better economy. This was then further developed, most notably by Chrysler with the "Hemi" - a cylinder form now universal, albeit now with four valves.
The 1959 Austin Se7en & Morris Mini Minor, first of the modern transverse-engined cars, set the pattern that would progressively sweep the World over the next 40 years - and counting.
Toyota Prius, Nissan Leaf, Chevrolet Volt and Tesla cars demonstrate we are nearing the tipping point to a new era by increasing the electrification of the powertrain of the automobile.