Facade defines a higher-level interface that makes the subsystem easier to use. Chain the receiving objects and pass the request along the chain until an object handles it. Given a language, define a represention for its grammar along with an interpreter that uses the representation to interpret sentences in the language. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently. The object will appear to change its class.
Strategy lets the algorithm vary independently from clients that use it.
Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.