The SNES also had a multi-tap, used to use it for Super Bomberman and Micro-Machines.
Currently DirectX9/10, Xbox360, and Wii all support up to 4 controllers. The Playstation 3 supports upto 7, but god knows how crazy that would be on a single screen.
The pioneer of Co-operative play was Perfect Dark on the N64 where you could play as 2 people playing through the game in a number of modes. This said it was the Xbox that really made this feature popular to the point where it now plays a heavy part in most FPS/TPS games.
Rainbow Six Vegas is the first I've seen where you can have up to 4 players playing co-op story/missions on any form of connection.
Here we have a splitter, so two of us play on one console; then a friend brought round her 360 we connected it to the network which is also connected online. So we had her as the 3rd and some yank on Live as our 4th. You just can't really describe the experience you get from playing through specialised missions with that many players and across such a diverse setup.
What surprises me is despite the PC having such capabilities for going on a decade now, it's never been taken advantage of. I find that a huge shame personally. Split-screen on PC games is almost unheard of.. I doubt many here being able to name more than a handful of games capable of it.
