Your middle-click mouse button — also known as your scroll wheel — can be an effective tab management tool in both Chrome and Firefox. Here are two shortcuts it can perform.
First, if you middle-click the refresh button on your browser window, it'll clone the current tab so you have a copy. If you want to get rid of that tab (or any other tab) just as easily, you only have to middle click that tab. If you'd like to see this in action, check out the video above.
Thanks for the tip, KatsumeBlisk!