I'm hardly free when you guys play, but if I were I'm down with any Doom engine game and mod combination. Using Doomseeker
online id Tech 1
games browser and Zandronum
id Tech 1 (doom engine) port finding online games, installing server required wads and game files and playing is pretty seamless. I play a minimum few hours a week.
id Tech 1 commercial games:
The Ultimate Doom (1995)
Doom II: Hell on Earth (1994)
Master Levels for Doom II (1995)
Final Doom (1996)
Heretic: Shadow of the Serpent Riders (1996)
Hexen: Beyond Heretic (1995)
Hexen: Deathkings of the Dark Citadel (1996)
Strife: Quest for the Sigil (1996)
id Tech 1 non-commercial games:
Chex Quest (1996)
Chex Quest 2 (1997)
Chex Quest 3 (2008)
Hacx: Twitch 'n Kill (1997)
Mega Man 8-Bit Deathmatch (2010)
Not to mention all the mods, custom maps and wad availble free to download.
For me it's between Alien Arena and Doom..