Lore? What lore?
Games with a lore so little, or outright nonexistant, that it becomes impossible to come up with a consistent story without theories.
1. Human Fall Flat
From Mansion to Ice, there's no plot. It's just you, some friends if you play in multiplayer, and the possibly most relaxing video game ost you'll ever listen to. Some of the hidden voices, the narrator in Mansion, or the fact that levels are named "dreams" could make a bit of room for theories, but aside from that, it's just a silly puzzle game where you play as a clay guy of dubious intelligence.
2. Insurgency: Sandstorm
There are grafittis across the maps, and details in cosmetics that hint to a small narrative; the insurgents are seemingly more of a rebellion group who wants the Security guys out through violence. Yet, there's no explanation of what started the whole conflict, or a deeper look of what the fuck is going on.