What is a good scary/horror movie to watch this month?

This movie for me cemented Sam Neill's acting range. From Dr. Grant with the dinosaurs...to this. This is also one of my favorite, if not THE favorite, sci-fi horror films of all time - which is kind of a tough genre to sell.

I love Event Horizon. I also love the theory that it takes place in the Warhammer 40k universe.

On the surface this comes across as SciFi, but it's a true classic horror with a scifi backdrop. It's essential watching for any horror genre fan, IMO.