Ougon Musou Kyoku
As a massive fan of the Umineko no Naku Koro ni sound novel series, when I first heard of a beat'em up based on it I was pretty psyched. The Umineko sound novels are intriguing mystery series based on finding out the truth about a numbers murders which occurred on a secluded island. The interesting thing about it is the narrative takes places as a argument between one of the victims and a witch to establish if the murders were committed by human hand or magic. It's lost of crazy meta-discussion in it, with wars of words taking place across planes of existence. Ougon Musou Kyoko is largely based on the meta parts of the original, and as such is mostly made of the anti-mystery witch characters.
The gameplay itself is rather unique. You pick a pair of characters for a team, which share a single health bar. You build SP to perform special moves for your partner character whilst the main one is fighting. The key thing is once you build up SP, you can declare meta mode to perform super attacks and other benefits, or you can cancel an opponent's attempt to declare meta. I'm no super beat'em up expert, but the gameplay feels reasonably deep to me. There aren't too many characters, only 10, but they all have their unique styles, such as Chiester's bow and arrow style, or Ange's summon style.
The thing that really impresses me about about Ougon Musou Kyoko is it's presentation. It's a doujin game developed pretty much independently, but it really looks professionally made. The music takes many cues from it's sound novel parent, as is to be expected. The graphics look brilliant, especially when compared to the sound novel. The game even has the professional voice cast from the anime adaptation. The story as always in this type of game is peripheral, but it manages to balance the hammy seriousness of the main game with a bit self-referential humour. It's not slapstick as Higurashi Daybreak is to Higurashi no Naku Koro ni, but it's all the better for it.
I really hope this game goes on to become a hit in the Japanese arcades like Melty Blood, so we can see further iterations with characters from the latter half of the series in it. I hear rumblings that it's going to be ported to the 360 at some point as well. It's a smashing game, and it's always nice to see 2D beat'em ups still knocking around.