The Testament of Sherlock Holmes is good. (Haven't played the newer one, but it's only 20% off anyway)
Divinity Anthology for $7.50 is a great price.
Runaway: A Road Adventure is a decent-ish point-and-click adventure game.
Another World is worth it if you're feeling nostalgic.
Game of Thrones RPG is okay if you like GoT. The story is good, the gameplay is not really. All of Cynanide's RPGs are pretty eurojank, but they're kinda fun if if you're not expecting much.