Clock Tower is one of those games that sounds really stupid in concept, but is freaking awesome when you play it.
Imagine being thrust into the role of a victim in a slasher movie, except you're not a total idiot. When the killer shows up, you can't fight him; you have to run off and hide/find a temporary way to disable him, or you're doomed to a new existence in two pieces.
However, while your protagonist is fairly intelligent (by slasher standards), the serial killer (known only as 'Scissorman') is also very clever. Despite not being very fast, he's good at finding ways to ambush you, ranging from jumping off the stairs, or hiding in places where you'd normally find plot-essential items or NPCs. Also, while there are a lot of hiding spots, only a
few are actually good. While you can hide under a bed or a bench, there's a good chance that Scissorman will suspect something and skewer you to your hiding spot. Using the same hiding spot repeatedly will result in the same outcome.
While the PS1 era graphics are a little weird for the characters, Scissorman has actually become creepier with age. His twitchy animation and unclear features make him more disturbing, and when he chases you, he loudly clashes his weapon of choice (if you haven't guessed, a giant pair of scissors), producing a horrible metallic clanging sound. His theme song is also sure to inspire panic. Sure, the voice acting is cheesy (it's a PS1 era horror game), and some of the characters are kind of stereotypical, but the atmosphere, music, and antagonist are all awesome.
Unfortunately, the series was driven into the ground by horrible sequels. Clock Tower 2 had some good ideas, but ended up being funnier than scary. Clock Tower 3 is an absolute riot only because of how ridiculous it is. Scissorman has shifted from being a menacing killer to an androgynous Soul Calibur villain. Don't even get me started on Lord Burroughs...
The biggest problem with Clock Tower is finding a reasonably priced copy anymore. But if you can manage to play it... you're in for a treat. Especially around this time of the year.