The games I play in the rift are
E: D of course
Assetto Corsa - Great experience, few issue that mean you can't play the game properly (i.e. campaign mode).
Grid Autosport - Better game than Assetto corsa but the cockpits are a bit rubbish and the driving is more arcadey, bumper cam is mental
Alien Isolation - Intense and I can only play for a short while before it's all too much, implementation of Rift support (not official) is a bit wonky.
Team Fortress 2 - Oldie but goodie, good rift integration and I actually seem much better at the game in the rift than a normal monitor, can make you feel a bit queasy
Half life 2 - Good rift integration but makes me queasy relatively quickly
Lunar flight - Excellent rift integration, nice game but there's not a massive amount to it.
Games I've got that I don't play a lot of.
Euro Truck sim 2 - last time I tried it there was a fair amount of stutter, weirdly likeable game if you give it a chance.
AAaaaa for awesome - OK game, good experience, find I get bored quickly though
Timerifters - excellent implementation, half decent game, not a great deal of depth though.
World of diving - performance is a bit spotty last time I tried it, still in development though, nice experience.
DCS world - looks pretty good but the menus are a bit wonky and I can't seem to get into it.
Star conflict - Free to play space dogfighting game, one of the best looking rift games out there (looks better than E: D IMO).
Snow - Skiing game, want to like this as I ski in real life, rift implementation was a bit wonky last time I tried it.
Trackmania games - Good implementation, can't seem to get into the game very much though.
Other stuff I don't try myself anymore but I show people that come round
Sightlines the chair
Titans of space
ZVR