If the diagonals of a quadrilateral are perpendicular to each other, the figure would always be included under the general classification:
$\textbf{(A)}\ \text{rhombus} \qquad\textbf{(B)}\ \text{rectangles} \qquad\textbf{(C)}\ \text{square} \qquad\textbf{(D)}\ \text{isosceles trapezoid}\qquad\textbf{(E)}\ \text{none of these}$
Note that a kite has perpendicular diagonals, but is not a subcategory of any of the existing answer choices. Therefore, the answer is $\boxed{\textbf{E}}$