MTA:SA 1.0

also comes with a feature that will allow scripters to have almost any idea created into a gamemode, not only this but this also supports upto 128 players in one game, custom objects and textures as well as scripted NPCs and much more. There is a full list in the readme, but overall this will probably make one of the best multiplayer modes for any of the GTAs (except perhaps GTA IV, although this one (SA) is probably more stable!) You can also have the Mario Kart 64 "Rainbow" track in game as well from looking at the screenshots !!! [b]Required Files[/b] Nothing
Here is Multi Theft Auto San Andreas V1.0, a multiplayer modfication for GTA San Andreas. This will allow for mulitplay action with in the game, including racing, deathmatches and much more. This