Perfect Dark. It did everything Goldeneye did but better. I loved all the options for multiplayer (and am frequently shocked that a lot FPS games have taken a few steps back in the multiplayer modes since then), I loved the weapons, story, voice acting, and coop was a lot of fun. It also so happened that at an age where my sister wanted nothing to do with her older brother, we would still do some bonding over a few games of Perfect Dark every now and then.