Following is a ranked list of scientific equations. The choice has been made based on popularity and impact, rather than on aesthetic appeal to me.
1. (chemical formula for water)
2. (Einstein's conversion of mass to energy)
3. (Pythagorean theorem for a right triangle)
4. (solution of quadratic )
5. (four building blocks of DNA with their matchings)
6. (law of gravitation)
7. (fundamental theorem of calculus)
8. (Ohm's law)
9. (radioactive decay of uranium)
10. (compound interest)
If you believe other formulas to take precedent, please send me mail
and I will consider your suggestion.