Two houses that are right next to each other (with the exception of maybe a cul-de-sac). Their sidewalks are parallel, their driveways are parallel, their garages are parallel. Most likely if it's a subdivision or a neighborhood built around the same time, their front and back doors will be parallel.
In the same theme of houses, your kitchen and bathroom sink. Both will shoot the water downwards. The water from your kitchen sink will not intersect with the water in your bathroom sink... until it runs down the pipes and into the sewers of course.
The sides of your TV, laptop, or phone. This one is obvious. Any of these items made where the sides intersect each other in like, the shape of an X or a t, simply wouldn't work. If you were to draw lines continuing from the sides of your phone from both the top and the bottom of it, the lines would never intersect.