A corner medicine cabinet is a good way to save space in your small bathroom.  Of course, the most logical arrangement is when it is placed over a corner sink.  The more open space you can create in the middle of a small room, the larger the room will appear, and the more comfortable it will seem when you're standing in it.

You would think that a corner medicine cabinet would have design constraints due to the limited use, but there is enough of a selection to give you more choice than you need.  You can literally see hundreds of styles on the internet.  There are narrower cabinets, taller cabinets, cabinets made of various woods, metal cabinets, mirrored and those without mirrors, and so on. 

Virtually all of the corner medicine cabinet options are deeper than your traditional, recessed cabinets.  Therefore, they give you more space and more freedom regarding what you put into them.

Reputable manufacturers include Broan, Nu tone, and (a bit pricey) Robern.  Kitchen and bath showrooms will probably have a better selection than the home centers.  For a broader feel of the styles and finishes available, I would Google "corner medicine cabinet" and you'll spend as much time as you like looking at different models. 

Once you've determined the style you like, go to the store and look at them.  You can't really tell about quality by looking at pictures.  Look at the hinging, and the material used to make the box behind the door.  Enjoy the process.