chmod g+u filename
chmod isn't the only command I screw up. In fact, my worst offender is "find" followed closely by ls, but when I screw up the options for those, at least something happens; not what I wanted, but something. chmod is unique for me because it produces a situation in which the command not only doesn't do what I want, it doesn't do anything at all.
I have a mental image of the system looking me and thinking, "Huh?"