A Rift isn’t handy right now to share screencaps, but preliminary tests show that the first Portal game by Valve has implemented Oculus Rift support! To get things working, activate the SteamPipe Beta feature in Portal’s configuration (from within Steam). Then add “-VR” to the game’s start-up parameters in the Launch Options. Portal 2 still doesn’t have signs of VR support, so it’s not worth trying yet.
If you have some good screencaps to share, please feel free to attach them.