While we're on the subject, something I well and truly can't stand:

Having layers that move faster than the ones above them. It breaks the laws of perspective, looks flat out wrong and has been done in more levels than I care to count. Technically JJ2 breaks the laws of physics many times, but that doesn't excuse the fact that it just looks plain ugly. The fact that it's so easy not to do makes it grind my gears even more when someone doesn't notice how awful it looks.