Black Mesa is a fan-made recreation of Half-Life. For people who don't feel comfortable with the possibly nauseating graphics of the original, I recommend this faithful yet featureful remake. 9/10.

Portal 2 includes a rich story to accompany the great humor on a journey through the ups and downs of Aperture Laboratories. The portal mechanics allow for very clever and interesting puzzles. 9/10

Garry's Mod is a sandbox game where you can do anything. The workshop has content you can add to your game with one click. You can play for hours and not get bored. Linux is well supported. 10/10.

TSP: Ultra Deluxe is a re-release. The developers prioritize Windows over Mac/Linux platforms. Natively supported. Additional content is very, very funny and integrates into the original content. 8/10