I ask the PCG staff a regular Weekend Question and post the answers on the site. If you'd like to throw in an answer here, I'll squeeze the best into the finished article!
This week's question is: What game would you never play without mods?
Obvious answer: Skyrim. How can you enjoy replaying Skyrim without being able to bypass the intro, sort your inventory by weight or value, or fly the paraglider from Breath of the Wild? OK, the last one is optional, but Skyrim is the number one game I would only suggest playing unmodded your first time through (The number two game is every other Bethesda open-world RPG.)
I guess if you count unofficial patches as mods the same goes for Vampire: The Masquerade – Bloodlines, but I'm thinking more of full-blown modifications rather than fixes.