Board Games
Concordia
Great Euro game with an easy teach because every turn you just play a card and do what it says on the card.
Dominion
A true classic, perhaps Quest for El Dorado is an easier teach but Dominion is better if you are going to play a lot, my most played game for sure.
Dune (the reprint of the old one, not the new Euro style one)
After playing games for 20 years a lot of them start to feel samey, Dune is so different to other games which makes it interesting but it's also a great war game which is rare. It's a lot of work to get a handle on the rules and I'm still working on it.
Planet X
This is mechanically "what if the game Clue was good?" as long as you don't mind the theme change.