Perfect Dark was an incredible local multiplayer game. 4 player support, plus support for 4 (?) bots where you could set individual difficulties and personalities, each player had their own independent menu in the lobby where they could tweak personal or match settings, a wide variety of weapons, maps, and game modes, there was so much in there.
The game also not only had a co-op mode for the campaign, but also an extremely rare "2nd person" counter-op mode, where a second player could take control of random mooks in the mission, jumping from body to body each time they died. There are extremely few games like this, one of the only other ones I can think of is actually Duck Hunt for the NES (you can control the ducks using the 1P controller).