What are your favorite Mac OS X keyboard shortcuts?

Solution 1:

ctrl+F2: Access the menu via the keyboard (Windows alt+space equivalent).

Solution 2:

Typing / on any file dialog will give you a "go to folder" dialog, which autocompletes with tab (you have to wait a second for it to work). This lets you type in the full path, from the root / folder.

Extra handy if you want to open from / save to hidden locations or already have the command line path you want to save something in.

This can be also accessed via ~ (i.e. the tilde key, to start from your home directory, e.g. ~/Documents) or using cmd+shift+G (which starts with the most recently entered directory).