One tip or trick per answer.
My favorite is
Opens the folder you're currently browsing in Finder. You can also pass URLs, images, documents or else to
If you specify a program name with -a you can pass the URL, image, document or folder to that program instead, e.g.
open -a Preview image.png, overriding the default program set for the filetype.
Please don't post duplicates. Search in the question like this:
inquestion:this ls -l
Mac OS X specific answers only.