Shower Light connected to bathroom ventilation fan. Does it need GFCI?
You need a fixture listed for wet locations: from the NEC.
Bathtub and shower areas. Luminaries located within the actual outside dimension of the bathtub or shower to a height of 8' vertically from the top of the bathtub or threshold of the shower shall be marked for damp locations or for wet locations were subject to shower spray. NEC 410.10.D. Since in a shower you will need a "wet location" fixture. Many call the main type of fixture used a "jelly jar" because it looks like a jar that is screwed into a fixture. There are many types that look better depending on what you want to spend.