Does anyone remember the old Rainbow 6 games?
Raven Shield was my favorite of the bunch. I've yet to play a better online shooter than that.
In Raven Shield, if you got shot it effected your movement or you would be killed. If you got shot twice you were dead. Now that completely changes the mechanics of a FPS. The first thing you do when you enter a map with your team mates is find cover and edge your way around the map. The game was tense, knowing that if you were spotted in the open you were most likely dead.
At the gear selection stage before the game began, it mattered how you kitted yourself out. You could go for full body armour but it would slow you, but allow you to take an extra hit or two. If it was a large open map and you went into battle with an Ouzi then you wouldn't be able to hit anyone more than a 20 meters away. If you had a sniper rifle then you couldn't hit anything close.
In contrast to todays shooters where the half map is filled with Rambo's running about all over the place and the other half with snipers. With the exception to battlefield which actually encourages team work modern FPS's all kinda feel the same to me.