Imagine marking your kids' clothing with markers to, well, mark them with your names so that your kids won't be confused. You put the clothes in the laundry, wash them and all, and dry out. While inspecting them, you find a big blotch of black stain spread all over your kids' clothes. OR, imagine this happening to your favorite golf bag. Oh no.

Of course the best way to go around this is to NOT mark the clothes. Why mark them, anyway, when you would know whose shirt are those. But, of course, one sometimes cannot help but forget these trivial matters especially when he/she has a demanding working schedule. So when this happens to you, you should make sure that your marker is suitable for laundry use. You cannot just use any kind of marker because using any marker might lead to blotches (like what was mentioned above) or they might just be erased after the wash.
You'll have to use markers that are specially designed for laundry use. Of course we have that kind of marker here in Office 1000. It is called the Sharpie Rub-A-Dub Laundry Pen from Sanford. Unlike ordinary markers, they neither spread ink nor fade away after washing. It stays there through washing and dry cleaning. Perfect for your purposes.
And while you are at it, also do consider this fabric marker from Sakura of America. Unlike the one from Safco, it has two tips (a fiber fine point and an extra fine plastic tip), which you can use on your will.