1.
Starsiege Tribes 1 : Renegades mod's mechanics related to movement and battle (jetpack flight, rocket jumping, shields, weapons, etc etc; can't narrow it down to one without the other...)
So far nothing has beaten the feeling of the Starsiege Tribes : Renegades mod Cyborg armor in CTF after you understand how the weapons, beacons, jetpack, tricks, etc work. Nothing has come closer to feeling like controlling a giant robot and it being amazingly cool lol [Hint: It isn't sUPPOSED to be a giant robot, but... everytime I play that game I feel the rush of adrenaline and freedom of piloting that armor.]
Gameplay : Take an armor that isn't supposed to move fast. Add jetpack, rocketjumping, insane distance non-linear projectiles, shields, rockets, all happening extremely fast... Best first person shooter I've ever played~
I only hope one day there will be a more advanced FPS, that will allow for freeform flight, so you aren't magically upright or dealing with retarded but funny ragdoll simulation stuff. I want the freedom of human flight without the consequences of messing up lol
EASIEST way to describe what I'm talking about : think of the Iron Man 1 movie, the big bad guy's armor at the end, trying to move around like Iron man
2.
Crescent Pale Mist : The battle system in that 2d game is wildly complex. The battles in that game on harder difficulties are just oppressive and exciting [and frustrating!]. Good indie game... (it's like a shump that's a platformer? Again, can't narrow it down to a specific type of move... but related to the freedom of movement while fighting.)
EASIEST way to describe it, a 2D Dragon Ball Z fighter that's a shump?!
3.
Grand Theft Auto (any game in the series) : Stealing vehicles lol
Not much to say except that it's just amusing to go insane in GTA, crank up classical music, while driving a semi while only looking through the rear view mirror view...... . . . .heh. ..h..e..h..
4. Chalk - the drawing
5. Braid - Time travel
6.
I dunno, will think about it some more... Perhaps I'm being way too general with my top 3 so called "mechanics"... but...