(In no particular order)

1. Solving quadratics: The skills I have acquired learning how to solve quadratics has helped me tremendously in all aspects of my math skills.  Learning how to factor has helped me not only in this unit, but the majority of the semester since it is one of the most useful skills in Math.  As well as learning how to use the quadratic formula, which helped me in my physics class and completing the square which was also useful in analyzing quadratics.
2. Solving rational equations: This is probably the most useful thing I learned in Math 11.  The improved skills in solving algebraically and utilizing factoring and common factors is probably the most practical thing in Math.  The most complicated form of solving I have seen to date, and solving is definitely one of the most useful skills in Math.
3. Sine and Cosine law: Learning these trigonometric laws are extremely useful since they can be applied to every triangle and not just right triangles.  Trigonometry is an extremely important area in Math because triangles are a crucial part of the real world in physics and engineering and learning these laws were extremely important.
4. Analyzing Quadratics: Quadratics are everywhere in the real world and knowing how to find the vertex, the domain, the range the scale factors and transformations were crucial to my understanding of quadratics.  This knowledge was crucial in improving my visual learning and visualizing graphs in Math and gave me a new understanding of how useful graphs can be both in Math and in the real world.
5. Infinite geometric series : Everything else on here is here because of how useful it is and how important the skills are, however I put this on the list because it was by far the most interesting thing I learned this year.  I find it so cool how we are able to calculate the sum of a never-ending, converging series.  I always thought that infinite was more of a concept and could never really be applied to anything, but when we learned how to calculate an the sum of an infinite set of numbers it blew my mind.