I think you're thinking of Slayers X: Terminal Aftermath: Vengance of the Slayer, which is not a shitpost but the greatest fps game ever made, you turd!
(It's a spinoff of Hypnospace Outlaw, which I highly recommend, especially if you're old enough to remember the internet pre-y2k because it's basically a very high quality pre-y2k Internet simulator. Also it doesn't use the same "S" but it is a parallel-universe version of it).