Project Eden didn't get a real following or praise, but looking back... I feel people didn't reallyappreciate what they had here. 4 player co-op puzzle game. Each character had unique abilities. It had a decent sci fi setting, and creative level design. The combat was'nt really that special, but I didn't really care. Its really old now, but I still enjoy playing it with friends.
Given the whole co-op game resurgence, I encourage people to give it a try.
There is a PC version too with LAN support. I just have the PS2 one with 4 player splitscreen.
Also, and im not sur whether this was really that hidden but... TENCHU!
Maybe not as tight as Metal Gear Solid, but a pretty fun stealth series.
There are also co-op modes. It can be a pretty tough game at times, but really worth it
for stealth and/or Ninja fans
Also...