There was a number of games that allowed similar things in these days. My favourite was San Andreas Multiplayer. All you needed was a copy of GTA: San Andreas and download the client, the server was community scripted. This gave birth to a number of unique servers: racing, deathmatch, role play, etc.

Multi Theft Auto (another GTA multiplayer mod, still alive today) allowed for similar things. And so did the source games (Counter Strike, HL2: DM, Day of Defeat, etc.).