Mine is Ludo: A solid 2 to 4 Player board game.
Fun Fact: It causes a war in Hindu Mythology.
Second is Chess because dev abandoned their game.
Clue.
It’s complex yet very simple. Can be played by a small or large group easily. Teaches logic, reasoning, and deduction over “outscoring” your opponent. Being the dealer doesn’t give you any advantages if you play it right. And because of all the various permutations of the cards, it’s always a new game each time vs a number of set scenarios/strategies.
I never got into Clue myself, though I blame Clue DVD for that. The premade cases led to a limited replay ability, sure, but due to these cases involving background narratives made you feel like a detective as you piece together alibis through story snippets.
It’s a shame they aren’t producing it anymore for quite some time now.
