If you are not a fan of Harry Potter, it's best to just click on the link to Martin Howard's collection web site (look to the sidebar). Otherwise, you might find out more about HP than you care to know...
From all that I have read and seen HP wizards tend to use quills. I heartily support the use of quills, but would there ever be a situation where a HP wizard would need to use a typewriter. Official MoM documents probably are written with a typewriting machine. O.W.L.s and N.E.W.T.S. were probably drafted with a typewriter before being sent to some sort of magical Linotype or offset printer. I believe there would be some situation where a typewriter would be used.
What type of typer would a wizard use? It would be easy enough to use a magical spell to make the machine work without direct manipulation from the user. In a situation where form need not follow any reasonable guidelines of usability, more eccentric and visually interesting typewriters would be the norm. The only visually interesting typewriter in my collection is a Blick 7. It has a magical pull on me, but there are some machines out there that would look perfect next to Dumbledore's Pensive.
Perfect for Ministry of Magic Offices, Hogwarts, Gringotts, etc.
Great machine for Dark Wizards. Voldemort has two.
Great for authors, homeowners, enthusiastic amateurs. Molly Weasley uses one. Bathilda Bagshot used a Ford to write her book A History of Magic
All of these images are from the Martin Howard collection. Take a look at his very comprehensive collection. Impressive.