Day Z mod
It's the clunkiest piece of garbage I've played since Blue Stinger on the Dreamcast. It's like a drunk and blind Mr Potato Head was rebuilt by a slightly retarded 10 year old and they decided to ask Lara Croft from the first Tomb Raider and a Picasso painting for its interpretation on how movements should be handled.
Skyrim
Super boring/dull/repetitive combat/quests/music/zones with outright pathetic audio design/fidelity. In comparison, I loved everything about Oblivion except its leveling system. I'm aware of the Realtek issue with Skyrim, that's not part of it. It's possible the game relies on simple FMOD implementation and players having a 5.1 system to prevent muffled audio playback and accurate dynamic range reproduction so the stereo mixes are terrible. If I shared what I truly thought of it and why it turned out that way I'd be harassed into Oblivion, pun intended. I also spent more time modding/maintaining the mods in case I ever wanted to give it more chances than actually playing it.