Changing the default X cursor.

[. .]

I'd like to change my default X cursor from the small black arrow to a 
crosshair.  The command "xsetroot -cursor_name crosshair" works, but for 
xterm windows only.  I've tried putting the command in .xinitrc and 
themes in .Xdefaults without success.

What works?  I simply want to see the crosshair cursor everywhere I now 
see the small black arrow.