1. Secret Hitler (or maybe Avalon, which is the strategically marginally richer, but harder to pick up, cousin of Secret Hitler). It's a highly adversarial, intense and fun game. The main downside is that you can't have a relaxed game of Secret Hitler and it tends to expand to take up the whole night (people always want one more game).
2. Code names; more relaxed game, fun even when losing. The main drawback is that it's language focused and everyone needs to have a good command of the English language (at least in the base version of the game), which can be a problem in more international groups.
3. Chinatown; easy to pick up and play even for people with no board games experience. The core of the game involves bargaining with other players and trying to strike various deals to trade resources. The game is designed in such a way that you rarely feel like you're losing - all trades generate surplus for both parties, so the core activity of trading feels very satisfying.
I have introduced the games above to multiple groups and, generally, everyone loved all of them. The one exception being Secret Hitler, as some people found it a bit daunting at first or didn't enjoy the intensity of the game. (on the flip side, others absolutely loved it)