I recently completed Penny Arcade Adventures: On the Rain-slick Precipice of Darkness, and I have to say that it may just be one of the best-written games of all time.
Let me start by saying I'm a huge fan of PA. Their humour is abrasive, but that's part of the charm. It's imaginative and high-brow, even while being so blue it's almost black. Gabe is a wonderful artist and Tycho is extremely intelligent and well-spoken. I'd urge anyone to give it a look.
The game carried the label "episode 1", so it's not surprising that the game is as short as it is, but really that's the only real detractor. It's downloadable off Xbox Live for about $20 in gamerpoints, and it's well worth it at even twice that price. The gameplay uses a traditional RPG format with turn-based combat. It's a simple system without a lot of frills, with a few mini-games added in to pull off special attacks and gain items. The soundtrack isn't vast but it definitely fits the themes at play. The script, including plenty of diologue trees, a little evilish voice-over and plenty of shocking comments, will have you laughing every 30 seconds.
Where this game really shines is the story. A Lovecraft-esque saga with some steampunk accents, it chronicles a character you design, and his (or her) search for answers and a home after his house is trampled by a giant Fruit-F**ker. Your character runs into two other characters (based off Gabe and Tycho) and joins their agency, Startling Developments. The characters are rich, shockingly funny and backed up by a full supporting cast. You travel through the suburbs, an evil carnival and other locals fighting hobos, mimes and other agents of evilness.
It's a simple game with simple controls and simple trimmings, but it's a hell of a good time and you'll want to play it again just to experience the hilariously dark, disturbing and disgusting events over and over again.
They've said this game took an enormous effort to make and after this series is done there are no plans for another one, but I really hope they release an action game featuring the cardboard-tube samurai.