I would like to consider myself a "mature" grognard that play D&D rarely. My focus is on playing other games that are set in modern times, APOC or sci-fi mostly. I really like to play the older 80s games.
Game systems that I once played years ago:
Aftermath the rpg
Metamorphosis Alpha the 1st edition
Boothill (any version)
Cyberpunk 2020
Current games that I play:
Mutant and Masterminds 2nd and 3rd Editions
Mutant Year Zero