The two most recent Deus Ex games, Human Revolution and Mankind Divided, have just gone DRM free on GOG. Human Revolution is the Director's Cut, which improves the original's crappy bosses but also removes the
piss gold filter. Don't worry, you can mod it back in.
Both games are also extraordinarily cheap at the moment, thanks to a coinciding Square Enix Sale. Mankind Divided is $4.49 (AU$6.79) and Human Revolution is $2.99 (AU$4.39).
Another Square Enix series joins GOG today too: Dungeon Siege. The whole trilogy is available, but only as a bundle. Don't bloody worry though, because the bundle is currently 85 percent off ($3 / AU$4.39), and of course, it's DRM free.