Games you'll never uninstall from your system.

[HoloDust]

It's usually:

Sid Meier's Pirates! (some version of it, depending on what feel I want, either original from '87, Gold from '93, or remake from 2004)
Combat Mission: Barbarossa to Berlin (2002)
Kerbal Space Program (2013)

I usually have War Thunder installed as well, but haven't played that in years.