These are the mods that I'm currently running together. They aim to improve the realism and immersion of the game. In addition, I dislike the default C79 and PO-4 scopes and reticles so I'm using realistic replacements.

Some of the mods alter the same files and should therefore be installed in a specific order. This collection is presented in the same order that I installed the mods.

Sound mods require a sound restart every time the game is launched. There are 3 ways to do this:
1) Manually via the console: Open the console (default key: ~), type "snd_restart" without quotes, and hit enter. This can be done in the menu or in a game.
2) Manually via a keybind: Open the console, type "bind p snd_restart" without quotes (replacing "p" with another key if you prefer), and hit enter. This keybind works in game but not in the menu.
3) Automatically via config files: http://steamproxy.net/sharedfiles/filedetails/?id=507784688. If the method in the guide doesn't work for you then skip steps 6 and 7 and do the following: put "exec autoexec" at the end of the "config.cfg" file and mark it as read-only. Note, however, that setting changes will not save as long as that file remains read-only.

Some of these mods use uncompressed HQ textures. If you have low system memory, they may cause the game to hang upon joining a server or occassionally stutter during game. Decreasing the paged pool memory in your video settings should fix that.