1. The problem asks which quadrilateral has at least one pair of perpendicular sides. 2. Perpendicular sides meet at a right angle, which is $90^\circ$. 3. The first shape is a tilted square or rhombus with all sides equal but no right angles, so it has no perpendicular sides. 4. The second shape is a kite or irregular quadrilateral with a clear right angle between two sides, so it has at least one pair of perpendicular sides. 5. The third shape is a parallelogram slanted to the right with no right angles, so it has no perpendicular sides. 6. Therefore, the quadrilateral with at least one pair of perpendicular sides is the second shape (the kite or irregular quadrilateral).