Simmons is a scientist working at Black Mesa. He is an assistant of Dr. Rosenberg, along with Walter Bennet. He escapes early on during the Black Mesa Incident when he, Walter, Rosenberg, and Barney Calhoun teleport to the surface through the use of an old prototype teleport, after which they escape using a Black Mesa SUV. Like his fellow scientists, his fate remains unknown.
 List of appearances
- Half-Life: Blue Shift (First appearance)