The Resistance: Avalon is a bluffing game that straddles the party game and board game genres. It is a variation on an earlier game, The Resistance, but Avalon has overtaken The Resistance in popularity. Board Game Geek currently lists Avalon as #1 in the party game category, an assesment that I agree with. Avalon requires 5-10 players, and takes about 30 minutes to play... depending on the group.
The game is themed, as you might guess, around Avalon, and the players are randomly, and secretly, assigned as either loyal servants of Arthur or vile henchmen of Mordred. But this is not really important -- absolutely no interest in Arthurian legend is required to enjoy the game.
The central game mechanic is ridiculously simple. Players take turns being the leader, and the leader's job is to simply pick a group to complete a quest. The table votes to approve or reject this group, and if they are approved, the quest is undertaken. The quest consists solely of the chosen questers making a secret vote as to whether or not the quest succeeds: one vote for the mission to fail is sufficient to scuttle the quest. And then the next player takes a turn being the leader, and the game continues. If three out of five quests fail, the bad guys win.
That's not quite all there is to the game, but that is the meat of it. Gameplay is centered around guessing who the bad guys are, or faking being a good guy, and arguing your point of view (usually loudly). The average player knows only what team they are playing for, and how many 'fail' votes appeared in the previous quests. It is surprisingly addictive.
There is a bit more to it. The bad guys all know who each other are, to allow for better plotting. One good guy, Merlin, knows who all the bad guys are -- but if the bad guys figure out who Merlin is, they can assassinate him, and that is an automatic loss for the good guys. And there is a limit on how many times you can vote down proposed questing groups.
And then there is even a bit more, if you want. There are four optional characters that make things easier for either the good guys or the bad guys. For example, Percival is a good guy who knows who Merlin is, making it much easier for Merlin's opinions to be spread around the group without him being assassinated. There are other additional gameplay options, but so far no group I have played with has felt the need for more that two of the additional characters, never mind additional rules.
As you may have gathered, I quite like this game, and moreover, most people who like board games tend to like this game -- it ends when you run out of time, not because you get bored. I have found that those whose idea of a game night is Rummikub or Scrabble tend to be a bit overwhelmed by Avalon, but this does not mean that it is a young person's game or an extrovert's game -- it is simply a game that requires, and creates, constant active engagement, somewhat akin to Pandemic, Spoons, or Ultimate Werewolf.
Avalon was created by Don Eskridge, and is available in game stores everywhere, and, of course, on Amazon and B&N.com. It generally costs between $15-20.