I recently switched from working in plain text files to working in rich text in TextEdit and one of the most annoying things about rich text is pasting from other types of windows. I like to use a fixed width font most of the time, such as Courier New. Unless I’m diligent and use Command+Option+Shift+V, I end up with a mix of fonts and font styles. I finally got fed up enough with it today to do something about it. This work-around will only work with pasting from the keyboard. It will not correctly paste text that has been dragged and dropped.

The solution is to use Keyboard Shortcuts to switch the Edit menu’s items for Paste and Paste and Match Style. It’s such a simple fix, I never thought to do it before now. After this fix, Command+V will paste and match style and Command+Option+Shift+V will paste (and keep the style the copied text was in).
Open System Preferences
Click Keyboard
Click the Shortcuts tab
Cli …

Source: Mac OSX Hints