del *.* (DONT USE THAT )
cls (clears screen)
cd {path} (changes the cmd dir to whatever path you enter)
chkdsk (checkdisk; checks the volume for errors (on next startup)
unformat {drive}: (unformats a formatted drive)
shutdown -{letter} (there are a lot of different things you can put in, but my favorits are -s (shutdown), -r (restart), -l (logoff), -a (abort shutdown) and more )
ren OR rename {drive:}{path}{dir | filename} {renameddir | renamedfilename}\
There are a whole lot more, and I don't have the time to list them. You can search google for more