Ao Oni

Another hilarious jikkyou play on nico, this time it's a poverty horror game made in RPGMaker called Ao Oni, or blue demon. The premise of the game is pretty similar to Clock Tower: you and your friends get lost in a big mansion and you have to solve some puzzles and find the way out, all the while getting stalked by a monster.

The guys doing the commentary on their playthrough are がみ(Gami) and ふひきー(Fuhiki), who are part of a group called Borzoi Project. They do a lot of jikkyous, but this is undeniably their most popular one by a large margin. They also have a fairly popular jikkyou of another RPGMaker game called Doraemon Nobita no Biohazard, which as its name suggests, is a crossover of Doraemon and Resident Evil.

The demon in this game is a big blue man who kind of looks like Obama if he was part of Blue Man Group. Sounds silly, but the game is surprisingly scary and the Ao Oni has quite a bit of personality. Gami and Fuhiki's reactions are priceless and their screams of terror transcend linguistic boundaries.



It's also been mirrored on Youtube
Playlist

FadedLily on Youtube is also doing an English translation of the Borzoi Project jikkyou, but so far he's only gotten the first 3 parts up.
FadedLily

Ao Oni has actually gone through several revisions. The version of the game that Gami and Fuhiki are playing is 2.xx, while the newest version of the game right now is 5.2. Every version of the game is extremely different from the others, too: different characters die, the endings change, and even the layout and size of the mansion changes. I remember in Ao Oni v1.0, three characters actually survive in the end, and there's a really scary segment where the main character look down a well and sees the Ao Oni frantically climbing up the rope with all its teeth out.

Ao Oni has apparently gotten so popular among English speakers that there's now a full English version of the game! It's for version 5.2, and requires RPGMaker to run properly.

Midori no Akuma

This is one of the funniest video series I have ever seen on Nico. They started in the end of 2008, but many English speakers discovered these videos in the middle of 2010.

To begin, it's a jikkyou play, which is kind of like the "Let's Play" series of videos that you see all the time on Youtube, where people commentate while playing through games. Two Japanese dudes commentate themselves playing through Super Mario 64. Except that they are playing the roles of 2 samurai from the Bakumatsu period, 坂本龍馬(Sakamoto Ryoma) and 西郷隆盛(Saigo Takamori). They speak in an odd dialect of 19th century Japanese, and talk of Mario-samurai's quest to defeat the Midori no Akuma(aka green demon).

Basically they invent a game within Super Mario 64 where throughout certain levels, they activate a 1UP mushroom and attempt to clear the level by gathering all 8 red coins and the star, while being chased down by the "green demon". Except that I remember the 1up mushrooms would actually run away from Mario when I played, so maybe this is something exclusive to the Japanese version of the game. In any case, it's quite a spectacle and it's amazing what that little 1up mushroom is really capable of.

Introduction and playthrough of Bob-omb Battlefield



Cool, Cool Mountain



Whomp's Fortress


Shifting Sand Land


Someone also uploaded them on Youtube as well
Playlist