Dark Sector, the ancient precursor to Warframe, is a pretty fun single player experience where you get a death frisbee that's lots of fun to fuck around with. Widely available.

Prototype has you play as an edgy bioweapon-infected antihero who eats people to restore his health and absorb their memories. Prototype 2 has a guy he infected on a quest to kill the first guy. Super edgy atmosphere and plot with ridiculously evil government black ops organization as the bad guys.

Breakdown is an OG Xbox game where you vomit up a hamburger in first person and get Dragonball Z powers. Reportedly it's playable on Xemu.