Just as there is an entire generation that can't step into a motel shower without remembering Marion's fate in Psycho, it must be difficult for a movie director to put a camera in a shower stall and not glance over his shoulder at Alfred Hitchcock. (And, in an era in which everyone, it seems, is armchair critic/scholar, I wonder who is more frightened: the Motel 6 customer or the director?)
Along those lines, I just saw De Palma's Scarface last weekend on DVD. The chainsaw murder in the shower overtly riffs on Psycho. What I found of further interest is that, in the DVD extra, De Palma (or the writer, Oliver Stone, I forget, and the second helping of Pinot didn't help), waxes proud on the grisly scene's lack of graphic violence: never do we see the chainsaw cut into the victim's flesh. The scene is revealed mostly through reaction shots of Al Pacino's face; the emphasis on implied violence is also a hallmark of Psycho’s shower scene, and Hitch made similar boasts. The main difference is that Scarface shower stall was drenched in living color blood (a scene that, perhaps, only Stone could have written) and the Psycho shower contained only a trickle of Hershey's syrup. I imagine Stone tipping his hat (or thrusting his finger) to Hitch and pulling out the throttle to accomplish what Hitch couldn't -- or wouldn't -- do.
If a director succumbs to the temptation to murder a character while in the midst of their most vulnerable moment—a shower—there are only so many angles to choose from. Nevertheless, there are a few shots that are effectively "owned" by Hitchcock in the way that "I've got you under my Skin" is owned by Sinatra: The POV shot of the shower head, the interior shot that reveals Mother stepping toward the curtain, etc. Any time a director uses one of these shots, a director will inevitably be compared to the Master of Suspense.