Stop. Or go.
As much as I dislike four-way-stop intersections, due to their inherent inferiority to roundabouts, I have come to understand and live with them. However, there is one thing which still infuriates me, and of course, this is because of the drivers, not the system itself. When I am on my bike, I often find drivers waving me through such intersections even when it is their right-of-way. This is annoying because
(a) it's not always clear to see what their hand-signal really means,
(b) it takes a long time to start on my bike and I can always tell the driver gets frustrated with me,
(c) I wish they'd just treat me like any other road user.