Paste without formatting

Command + Shift + V

Reveal desktop

Cmd + F3

Create new directory

(If the parent directory is too full there's nowhere to right click)

Cmd + Shift + N

Switch between two windows of the same app

Command + `

Show/hide hidden folders

Command + Shift + .

Change default column width

Alt (aka Option, ⌥) + Drag Width

Change default app

​RCDefault lets you change the default application by e.g. file extension. When you install, it gets added to your system preferences panel

Add custom app shortcuts