Perfect Dark
Pretty sure my co-op buddy has lost interest in this, and so have I (in the single-player, anyway). I'm glad to have the game around for online multiplayer, as infrequently as that might come up; I'm still pretty impressed by how much fun the Combat Simulator is. But the campaign feels pretty antiquated, in light of ten years of industry sophistication in such areas as checkpoints, in-game directions, and maps.
Progress: Gave Up -- Saving the President