Here's a good one for your intermediate to advanced English/ESL/EFL students if they need to practice free-flowing narrative writing and/or medical vocabulary.
It's simple: Put students in groups of four and give them each a copy of PAGE ONE. Assign them a scenario from the handout and have them write the first two sentences of a story using some of the suggested vocabulary. After a set amount of time, tell them to pass their papers to the write and continue their classmate's stories. Keeping passing the stories around until each student has contributed at least once to each piece of paper.
You'll be surprised at the often outrageous tales they invent!
ENRICHMENT: Afterwards, practice proofreading by having different groups edit each other's stories.