I was trying to think of which games created certain mechanics that became popular and copied by future games in the industry.
The most famous one that comes to my mind is Assassin’s Creed, with the tower climbing for map information.
Operation WinBack from 1999 is considered the first third person cover based shooter.
Showing my age here, but what’s the difference between hiding behind cover in Gears of War vs what we did in LAN parties for UT or Wolfenstein 3D?