Normal multiplayer in Quake 2 just sucks ass and so do most of the mods available for it. Fortunately some of them really hit the spot. Action Quake 2 differs from other mods with it's realism.  You can kill with a single shot but hitting isn't as easy as one would think. Shooting while running causes bullets to hit everything except your target. And when you get hit, there's no way of getting health back. AQ2 has custom skins, models, weapons, sounds and maps. AQ2 makes you play the game with a totally different strategy if you plan to stay alive. Perhaps this explains the enormous success AQ2 has had since it's first appearance. 

The gameplay

Firt of all, it's a lot harder to hit anyone than it is in normal Quake 2. Accuracy depends on your position. If you run, you are extremely inaccurate. Slowing down to walking helps a little but you will hit much better if you stand still. While crouching, aiming is as accurate as can be. But be warned, staying still makes you an easy target for others so it's better to seek cover quickly. Aiming is a bit different with each weapon but more about that later. Because AQ2 has a certain degree of realisim, you won't be able to take much damage and wounds keep on bleeding until you bandage or die from it. For example a hit in the head with ANY weapon leads to death. A shot in the chest causes more damage than a shot in the stomach. Legshots are particularly annoying. Though it doesn't do much initial damage, you start to limp which is a very bad thing if you need to get away. Falling damage is greatly enhanced so jumping of buildings may cause serious legdamage or even death so watch out. Note you can only carry one unique weapon & piece of equipment at a time. Some servers do allow to carry two unique weapons. You can drop your unique weapon or item to pick up another. Very handy if you run out of ammo.

Modes of play

There are currently two modes of play: deathmacth and teamplay. Deathmatch is very much like deathmatch in general with exception that you can't regain health. This makes it a bit more challenging and at the same time more rewarding: If you get enough kills in a row without dying, you get more frags per kill. After four kills, you get two frags per kill. After eight kills, you get four frags per kill and so on always doubling the amount of frags.  In deathmatch you start with a pistol and a knife, nothing more but that's enough to take out anybody. Weapons and equipment are scattered around the maps, usually only one of each kind. Teamplay is a much more interesting mode of play. First you choose from two teams. After that you choose one unique weapon and one unique piece of equipment in addition to your pistol and knife. Then when the game begins, your objective is to eliminate the other team. If you get killed, you have to wait until the beginning of the next round. 

The Files

These are required to play:

Quake 2 v3.20 update
Action Quake2 v1.0c

You may want to grab these two fixes:

Fix-1
Fix-2

AQ2 has custom commands and you may want pre-made cfg:s

LaXu's AQ2 Config v12.8
A-team's Config examples

Mods for the mod:

AQ2 Single player
Bots for AQ2

And just for backup:

The original Gamex86.dll