Shadow of the Colossus. It's a game with interesting ideas and was technically ambitious, but I did not enjoy it at all. Boss fights are usually the part of a game I like the least and it's basically just boss fights with long uneventful horse rides in between.
No hate, no dogpiling, just curious. For me, it's Skyrim. Don't know why, considering it should be exactly my kind of game, but it just didn't click for me.