Remap command-arrow key to the same as ctrl-arrow keys (moving by word)
You can change the default keybindings for OS X text editing with the DefaultKeyBinding.dict file. Make a new text file at ~/Library/KeyBindings/DefaultKeyBinding.dict, with these contents:

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
&lt;plist version="1.0"&gt;
&lt;dict&gt;
    &lt;key&gt;^&amp;#xF702;&lt;/key&gt;
    &lt;string&gt;moveWordLeft:&lt;/string&gt;
    &lt;key&gt;^&amp;#xF703;&lt;/key&gt;
    &lt;string&gt;moveWordRight:&lt;/string&gt;
&lt;/dict&gt;
&lt;/plist&gt;


Restart or log out and in, and controlleft and controlright should do what you're looking for. This will work in most OS X apps, but there are some (typically third party text editors) that use their own bindings, which will need to be switched on a case-by-case basis.