As a big horror fan, this is a tough one. The Texas Chain Saw Massacre is a masterpiece and continues to unsettle even after multiple viewings. Everyone knows Poltergeist and Salem's Lot but a couple of his lesser known movies that I love are Eaten Alive and The Funhouse. Thanks for the scares, Tobe!
This is a real bummer. One of the underrated giants of the horror genre. The last thing I saw from him was an episode of Steven Spielberg's sprawling multi-generational alien abduction story, "Taken" back in the early 2000s.