Phobia (1980) is a low-budget horror film about a psychiatrist facing the ever-growing possibiliy of losing his innovative treatment program as each of his patients are mysteriously being bumped off, one by one, in ways that relate to each of their biggest fears (e.g. agoraphobia, claustrophobia, etc.).

Reasons as to why this film should be riffed on:
1) It was directed by John Huston, a name that the RiffTrax gang is very familiar with, so the riffing possibilities there are endless
2) The film stars Paul Michael Glaser as the lead, making room for as many references to "Starsky and Hutch" as possible, as well as other things he has done
3) The quality of the film reel (as well as the quality of the film as a whole) makes the latter look more like a TV movie rather than a major motion picture studio release (in this case, Paramount Pictures (https://www.youtube.com/watch?v=xDTdDL0xFOU)), so you know right away that it's not a masterpiece by any means