Let's See...
-Serious Sam (Series): Got a bundle deal in the Steam Christmas sale, and while I already owned the HD versions of TFE and TSE, I'm actually enjoying playing through the classics. Just recently finished BFE, and will get started on #2 after I beat The Second Encounter. Oh, wait, I need a description; KILL EVERYTHING.
-Clock Tower: This game is going down alongside Bioshock and System Shock in my book, where I actually have large portions of the game committed to memory due to how often I replay it. It's a late 90's point-and-click adventure game for the PSX (it's nowhere near as awkward as it sounds, believe me). It follows standard adventure game layout, save for one interesting twist; at any given moment, an immortal maniac with an immense pair of shears (aptly named 'Scissorman') will burst out of nowhere, accompanied with the most adrenaline-pumping theme music you'll ever hear. Now, since you play as a teenage girl or a middle aged psychiatrist, and since Scissorman is invincible, your only option is to run, hide, and pray that he doesn't find you. Also, if you pick a place that's really obvious (under a bench, under a bed, etc.) or somewhere you've hidden before, he will notice, and he will impale you. Now, the 90's horror game cheesy voice acting and corny writing are abundant, but Scissorman redeems it in full. Think of it as a distant relative to Frictional Games' works. Except without the Lovecraft. Just scissors. Really big scissors.
-Duke Nukem 3D: I always have a session of an old FPS going in the background in case I end up with nothing to do, and don't feel like playing anything else. You play as the singular most badass man alive, and fight aliens who are trying to steal our women. And you can run at nearly 60 mph. while kicking one leg constantly at a ridiculous height and holding a 50 lb. RPG all at the same time.