Here are a few (in no particular order):

- Dynamic Programming

- Graph algorithms: Traversal (A*), shortest path (Dijkstra, Bidirectional, Floyd–Warshall), minimum spanning tree

- Recursive Search Techniques

- Search Trees (binary, n-ary, splay, AVL)

- Suffix trees

- Parsing using regex

- Sorting (with all the variations)

- Hashing

- Greedy Algos

- Divide and conquer

- Genetic algorithms

There are a few other algorithms that are must-know too. I guess that would depend on the domain we are in (computer vision, machine learning, NLP, etc).