I've had the opportunity to play Codenames with two different groups, now, and it's great. It's one of those concepts that sounds super-easy when you describe it, but which turns out to be extremely challenging once you're dropped into the hotseat.
It's a highly social team game, in which two spymasters try to communicate the secret code names for their field agents to the other members of their teams. Mechanically, this is a 25 x 25 grid of small cards with simple words on them: dragon, button, castle, car, spring, ocean, elephant, and so on. The two spymasters have a secret card in front of them which tells them which words indicate a member of their team, a member of the opposing team, a handful of innocent civilians, and one very scary assassin.
The spymasters take turns giving very a very simple clue: one word, then a number. For example, from the word list above, they may notice that castle and dragon are both their team's code words, so they might give a clue pointing to both of them. They might want to say "fairy tale", but that's two words, so they rack their brains and settle on "fantasy, two". The team then selects words one at a time. If they get one right, they can then select another one.
If anyone ever selects either an agent of the opposing team or one of the innocent bystanders, their turn ends immediately. If they ever select the assassin, then bam, they lose the game. That simple.
The assassin is perhaps the most interesting element in the game. We had one game, for example, where the assassin was on "octopus". By chance, there were a bunch of other ocean-related words, like "wave", "seal", and "beach", but both spymastered steered WELL away from anything aquatic-sounding, out of fear of the assassin being picked.
The simple, slow option for the spymaster is to pick a single card, give an obvious clue, and just trundle along getting one card per turn. The riskier but more profitable option is to try to get two, three, or even more cards in a single turn. When the latter strategy goes well, a team will win by a big margin, when it goes badly, it can backfire massively. I have seen a game in which one team had a full half of their cards revealed by the OTHER team making mistakes.
I highly recommend it. It's a social, chatty game that will greatly test your poker face (once the clue is given, the spymaster cannot point, shake their head, grunt, or anything, even if somebody looks set to pick the assassin) but unusually for a word association game, there are some depths of complexity and strategy to it that are not apparent on a first play. It is also massively replayable, owing to its relatively few components being able to come out in a profusion of different permutations.
Oh, it's quite cheap, too. I got it from Oz Game Shop for $30 with free postage.