Enemy Zero, a SEGA Saturn and Windows stealth title with invisible enemies the entire time through, whose location and strength were determined via sound heard through the game. While not for everyone and I easily understand why no one has done it since in video games (Audio Games have, but that's a different medium), it's a hell of experience the first time marred by some questionable design choices elsewhere in the game that dragged the whole thing down, but never the concept.
I easily imagine someone could make a wonderful title these days with all the advancements in sound technology for crispness and quality, not to mention comfort of headphones. If on speakers, for once the whole surround sound "you can hear it coming behind you" would actually make full sense.
illbleed had a great and fun system for those that figured it out and didn't mind the silly spectacle that was the game. In the title you were presented with a user interface indicating the main senses of the body such as sight and smell to help you figure out scare traps inside a horror theme park. In a simplified sense, this was a horror themed Minesweeper in 3D geometry as you had to figure out which were the traps and which were perfectly safe.
Now the game was great fun and a delight for the absurd, but suffered from the era of Resident Evil like controls and presentation for horror games plus poor and stilted combat, but as a gameplay mechanic and design choice, the horror monitor and spotting the traps was brilliant and could easily become something great (albeit it niche) product today.
A Boy And His Blob's Hug Button. I don't care what anyone says, every game could use a Hug Button and be better for it. EVERY GAME.
Speed Racer for PS1. Right, so rather par at best as a racer, but it featured the trademark Mach 5 and all the gadgets that came out of it. Race courses could have short cuts a normal racing vehicle wouldn't make it through, but the Mach 5 could simply have buzzsaws in front to cut down the trees to get through or use hydraulics to make it bounce/jump over a cliff. Witch the direction titles like Dirt, MotorStorm, and others were going I thought we might get another along this idea, but alas it never happened.
Resident Evil 6's Onslaught Mode. Now I'm no fan of Resident Evil 6's story or playing through that aspect, but Onslaught Mode is truly amazing if you get a chance to play it with someone else who got to know the ins and out of the combat system.
Onslaught Mode for those that don't know is a competitive mode best compared to Verse Mode in Puyo Puyo or Tetris, but instead of taking out blocks and sending garbage to your opponent, you kill the various monsters and unleash more for your rival to face.
Chrono Trigger's Position-based Turn-Based Combination Combat system.
While not the exact same type, the
Grandia series is a wonderful series for position based combat with turns.
It also has a wonderful magic system where one gains new spells not by simply levelling up or buying with skill points, but by repeated use of that type of magic. Use Fire a lot, gain new fire spells.