In the Navigation editor in Admin it would be nice if you could have a Checkbox to “Open in New Window”.
I have a Donate Now link that goes directly to paypal for our non-profit. I also have a donations page within the site with more information like linking to wish lists and other options like mailing a donation.
I know this is a limited use case and I could just modify the template for this one menu item that needs to open in a new tab/window.