Obviously serious code considerations here. A basic recessed can is the best option in my opinion. If it is a retrofit, get a remodel type can that snaps on to your drywall and be sure to get a trim that is UL rated to be in a wet area. Otherwise, you can go with surface mount units, your selections will be a bit more limited being you need the UL rating.
Becky is correct. Use a remolders housing if no access above the ceiling. If you have access, you can use a new construction housing. The trim will be either frosted glass or opaque plastic and most likely limited to a 60 incandescent lamp.
I wanted ligting wish someone would have told me this, the excuse was because I had no access in ceiling, great question Scott and great info Becky
You can install surface light as long as you cannot touch it. So if you have a high ceiling within the shower area surface mount is ok, But there are clearance requirements that must be adhered to for safety.
Light fixtures greater then 7'6" above water OK if GFCI protected Rated for damp location and no exposed metal. The wall switch cannot be within five feet of the shower door opening.
A insert light between the framing above is the best to use. You can get these with lights and fan combined so it will remove the steam before it gets all over the rest of the bathroom. Simply snake the vent along between the joists to the outside and install vent grill there. You can purchase a combo GFCI switch for the necessary protection in this area.
I have access to the electricity and will need a sealed can light.
If you are worried about wiring, you could always get a wireless motion sensing ceiling from mrbeams.com. They cost $24.99 and can be mounted with screws. The light is really bright and it comes with a light sensor that can easily be removed. I found mine at http://www.mrbeams.com/products/ceiling-light/mb980-mr-beams-wireless-motion-sensor-led-ceiling-light.html.