One of my all time favorite multiplayer games was Goldeneye 007 on the Nintendo 64. Many of my high school days were lost to the pure joy that was Goldeneye 007 multiplayer! It seems the game has left a mark on quite a few other people as well. So much of mark that they have made a Half Life 2 Mod to recreate the Goldeneye experience.
Goldeneye Source is a multi-player (with limited single player) mod for Half Life 2. It features many faithful recreations from the original Nintendo 64 version. There is plenty of servers out there running the mod and the action in game is intense.
So step back in time with me a bit and indulge into a bit of gaming nastalgia. Enjoy!