Having read the other comments I am now ready to set forth a group of lists - covering discoveries and inventions - with such diverse items that it is hard to compare. Also many beg the question which is more important, the basic research or invention of an indispensable component or the final assembly.
Basic Living
1. Language
2. Clothing
3. Agriculture
4. Wheel
5. Fire
6. Writing
7. Mathematics
8. Crapper/toilet
Health
1. Germ theory of disease
2. Vaccination
3. Antibiotics (one could argue for the more specific like penicillin)
4. Birth control methods - more specifically the pill
Mechanical Power and Transportation
1. Steam engine
2. Train
3. Steamboat
4. Internal combustion engine
5. Automobile
6. Airplane
Electical & Electronics
1. Electicity
2. Lights
3. Telegraph and telephone
4. Vaccum tube/diode
5. Radio and televsion
6. Computer
7. Transistor
8. Internet
9. Communications technology