I've been using the same "The Matrix" screensaver since, I think, Windows was born. This one: http://www.meticulous-software.co.uk/downloads
It's pretty cool and definitely the best Matrix screensaver out there. I know. I use "The Red Pill" on my Macs and the ones that are on my Linux box are pure crap. I've had to resort to making my own screensavers on the Linux machine.
However, in this day and age of 64-bit Windows 7, my 32-bit "The Matrix" screensaver is becoming a little long in the tooth. What are you guys using? Anything really, really cool that'll show off the awesomeness of an 8-core cpu/8 GB RAM/1920X1080p rez screen?