This is such a no-brainer, as a way to set up a first sequel, in a horror or action franchise. Set it in a hospital! It's the most logical place to set a first sequel, because at least one or two characters that survived the carnage and mayhem of the first movie in whatever the franchise is probably end up spending at least a little time in a hospital.

What are some franchises that come to mind for you, which employed this device? It doesn't necessarily have to be horror, although that's best, of course. Also, the hospital could be either a regular hospital or a mental hospital. It doesn't have to be set entirely in the hospital, but at least a scene or two at the beginning have to be in one. Here are a few movies to get started:
--Halloween 2
--Terminator 2
--Hellraiser 2 (I did a typo there, and typed Hellraider... that could be a pretty cool movie, actually)
--Phantasm 2
--NOES 2 (no, 3... whatever, I'll sneak it in here)
--Grave Encounters 2 (well, duh)

Now, how about any franchises that SHOULD set a sequel in a hospital. Anything come to mind? I'll start:
--The Departed
--Commando
--Hot Shots (Part Trois)
--Robocop