Remove custom formatting from a sitcky (OSX Stickies)

Just remember to press Cmd-Opt-Shift-V (Paste and Match Style) when pasting and you won't need to reset it all the time.

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If you still want to reset:

1. Cmd-N to make a new temporary Sticky with default formatting,
2. Cmd-Opt-C to copy formatting,
3. Cmd-W to close Sticky
4. Cmd-A to select all
5. Cmd-Opt-V to apply (default) formatting (i.e. clear).

Alternatively press the following sequence to copy all content of a Sticky into a new one with default style:

1. Cmd-A,
2. Cmd-C,
3. Cmd-N,
4. Cmd-Opt-Shift-V

Using AppleScript and Automator you could create a Service that automates these keystroke sequences.

Its not a full solution to what you asked (5 years ago), but with custom keyboard shortcuts, its possible to easily remap Cmd-V.

On El Capitan:

Go to: System Preferences, Keyboard, Shortcuts, App Shortcuts.

Plus sign to add a new shortcut.

Change the Application to 'Stickies'.

Menu Title: 'Paste and Match Style'

Keyboard Shortcut: [Press Cmd-V]

This is very similar to the accepted answer, but less keystrokes on a day to day basis.