Adding the "Null" operand to the Select by Attributes form in ArcMap would be a nice addition. Currently using only mouse clicks, I can construct a query where a value is...(and then have to type NULL). Simple fix, just add it to the form.
This idea has been merged with Add "Null" and "In" buttons in the Query Builder.
BTW, this ideas forum is a great addition to the support site. Nice work!