We picked Team Fortress 2 as the game - the reason why is a whole different story I won't go into here. TF2 used the Source 1 engine, and as it happened two Valve games also using that same version of the engine were Half Life 2 and Portal 1. So as a side-effect they also got to work in VR.
Well, Portal 1 "worked" - but all the tricks with perspective when you went through a portal were of course a nauseating disaster - it was pretty unplayable.