If you are a Google Chrome user who is used to the CMD-Shift-T keyboard shortcut to reopen your last closed tab, there is a Safari equivalent that is not very well known. All you have to do when you close a tab is press CMD-Z (the normal Undo shortcut) and the tab that you just closed (or accidentally closed) has now been reopened! For some reason, Apple decided not to publicize this feature, but now you know about it and can use it to your advantage.
Questions or requests? Post them in the comments below!