The worst is a few tools where when you type:

    the_command -foo

...and the tool responds with:

    -foo: No such option. You probably meant --foo

Well shit! Thank you for that burst of empathy. If you, developer, are that confident that's what I meant why couldn't you just make both inputs do the same thing? You went out of your way to make the code handle -foo, but only to have the program fire off that snide remark instead of doing what you know the user meant to do. Maddening.