Ctrl+H.
Also,
Open any file quickly without browsing for it in the Package Explorer: Ctrl + Shift + R.
Open a type (e.g.: a class, an interface) without clicking through interminable list of packages: Ctrl + Shift + T.
Go directly to a member (method, variable) of a huge class file, especially when a lot of methods are named similarly: Ctrl + O
Go to line number N in the source file: Ctrl + L, enter line number.