StrikeThrough extension for Gmail
Get This Chrome ExtensionUntil now it was quite tricky to add strike-through text to your Gmail messages. Now you can add strike-through text thanks to this extension. Install this extension in your browser and refresh the Gmail page. The button is immediately available in the Compose Window.
Select the text in your compose window and click on the newly added strike-through button.
The extension supports keyboard shortcut Ctrl+Shift+S. Select the text and press Ctrl+Shift+S. You can toggle the text style by pressing Ctrl+Shift+S again.