Repeating a command you just carried out is a surprisingly useful thing to do, yet most people are completely unaware that bound to C-x z is Emacs’s repeat command.
Like the . command in vi, the repeat command will repeat the last action, skipping any input events (like character input.)
To save you from press the rather awkward keybind every time you want to repeat something, you can repeatedly press z after your first invocation to call repeat. Of course, you can also use the universal argument to repeat the command N number of times.
As I mentioned in my article on Mastering Keybindings in Emacs, you can also repeat (and edit!) complex commands like query-replace-regexp by typing C-x M-: or C-x M-ESC.