What exactly do you mean by 'Design'? Game Design or are you rather referring to presentational aspects?

For starters, Carcassonne is great for having simple yet elegant rules. Short and easy enough for every taste and rather quick sessions.

Netrunner is my recent favorite. Love that dystopian cyberpunk theme & great game design. Pretty deep though.

The entire Arkham Horror series ist pretty cool too, a bit complex though + it's more interesting if you know a bit about the H.P. Lovecraft universe

Another good yet nerdy one is Twilight Imperium. The artwork is a bit cheesy, but the game is pretty awesome if you have some time