Half-Life 3? Portal 3? The Half-Life/Portal crossover that was hinted at in the second installment of each?

Source: https://games.slashdot.org/story/23/02/13/2310217/valve-is-working-on-a-major-update-for-team-fortress-2?utm_source=rss1.0mainlinkanon&utm_medium=feed

I spent two days roaming around town, drinking my fair share of the Half-Life Hefe, and hiking the White Bluffs Overlook above the Columbia River, which was once home to the Native Wanapum and Nez Perce.

Source: https://www.counterpunch.org/2023/03/17/a-bad-trip-to-the-most-radioactive-place-in-america/

That said, he believes a first person shooter/real-time strategy hybrid set within the Half-Life universe codenamed Citadel is still in the works.

Source: https://metro.co.uk/2023/02/03/half-life-3-cancelled-in-2015-as-story-and-gameplay-details-leak-18218191/

Unfortunately, some great video games miss the mark and waste their potential, like Half-Life and Marvel's Avengers.

Source: https://www.cbr.com/gaming-series-wasted-potential-lost-opportunities/