My first FPS is Wolfenstein. Not all those cheesy add ons but the orignal first one with all 100 floors. Before doom, before cod, before moh, The orignal FPS. "guten tag" anyone?
My first MP is ofc Cod United offensive. First cod to have a default sprint
Best things about it, spawning with deployable MGS, JEEPS!!!+tanks, iron sight bolt actions, and game mode Base assualt. Killstreaks werent based offa kills/p life, but total overall kills. Having 40 total kills lets you call in mortars every 5 minutes. 10/20/30 kills let you spawn with grenades,smoke,pistol, and stachel charges. And no perks or custom classes or UAV or anything, just you and your rifle. (anti-tanks weapons are found throughout the tank maps)
That and an awsome, awsome modding community which released the first MP zombie mods for cod. (designed for coduo and regular cod) and more maps than could fit on your computer.( most of them pretty good)
Just to bore you even more, they had a fun mod. A map full of obstacles, jumps that can take minutes to get, ladder-to-ladder jumping, portals, and sneaky respawning tripwires, you get a pistol with one clip and the ability to save and load spawn positions. First person to the end stops the match.
Add all that to servers with up to 64 people, you get some huge, huge ground wars. 32 vs 32 is extremely hard, even on maps 25x the size of nuketown.