You can now grab Ubisoft's first-person-shooter XIII for free as part of GOG's Spring Sale. That's the good XIII, by the way, not the recently released XIII Remake, which is so full of bugs you're best off avoiding it at all costs.
Originally released on the Nintendo GameCube, PlayStation 2 and Xbox in 2003, XIII is a quality (and sometimes frustratingly difficult) espionage game that's loosely based on the Belgian graphic novels of the same name.
It brings the visuals of the graphic novels to life, filling the screen with comic-book-style panels when you whizz a throwing knife into someone's face and phonetic visuals for sound effects, whether that's the TAT-TAT-TAT of chugging through machine gun clips or the approaching taps of enemy footsteps.