Here's one that maybe you don't use everyday, but you should. Some commands work better in rapid succession. I place receptacles in building 30 at a time. In the old days I would select the duplex tool from my palette, place a receptacle, select the tool again and place another one, and so on and so on. These days I invoke a little known beauty call Multiple.
Multiple is a command that will repeat any other command until the user escapes out of it. You type in Multiple on the command line and AutoCAD asks which command you would like to repeat. I have a lisp to insert a receptacle at the proper rotation, scale and layer. I combine this with the multiple command in a macro to machine gun in as many receptacles as I want.
Just in case you were wondering, if you invoke multiple and ask it to multiple multiple times, the universal does not explode. AutoCAD will not allow you to invoke a multiple in a multiple.
Yeah... I tried it.