Multi-Tap for the PS2 & PS1
Buyer Beware!
It didn't work for all of my PS2 games that supported multitap.  I have the PS2 slim version, and I found that I have to unplug and replug the multitap to get 4 players to work for Hot Shots Golf Fore, and it just didn't work at all for Smash Court Pro Tournament 2.  I'm probably not going to buy any other multiplayer games for the PS2 from now on.