HL:A gravity gloves. Solves the problem of reaching objects at a distance quite elegantly.
Phantom: Covert Ops and Kayak VR, the kayak-locomotion just works so well, better than anyone would expect before they try it out.
Synapse's handheld minimap. A simple idea and works better than HUD minimaps.
Population: One, height calibration. It sets a max height as a reference point to apply IK to the avatar when the player crouches, which is necessary for a competitive shooter game. The way it's set is also quite neat: when the game launches, you are prompted to look at the text saying "set height" and the progress bar will load when you keep looking at it. No button press required.
I can't help but be impressed by the swinging mechanics in Swarm and Swarm 2. The way you can move and spin around is incredible, and surprisingly, it never made me feel motion sick. I haven't experienced that kind of freedom to explore and shoot in other games with similar movement.
The hand based zero g movement in the Lone Echo series and Mission ISS. Pulling yourself around by grabbing the environment was cool. Although Mission ISS did it better since it supported rotating by grabbing with two hands.
