I think we all know the problem: you’re browsing the web, opening dozens of tabs. After a while you start closing them again – but damn, that one was still important. So you head to your history, and start searching. Well, you can do that. A much faster way is to just press ⌘⇧T and the tab is back again with its full history.
This should work for all major browsers – I have tried Safari, Chrome and Firefox on a Mac. All of these support the shortcut (on Windows it should be the same but “Ctrl” instead of ⌘).