Hoshi no Samidere which is often called Lucifer and the Biscuit Hammer. The main character is Amamiya Yuuhi, a college student who is one day called to participate in a battle to save the earth by a talking lizard. Of course he wants no part in this which sets the tone for this off-beat adventure story.
The basic premise for this story is that the world is threatened by the Biscuit Hammer, a massive hammer floating is space, and 12 Knights have been chosen to help the Princess fight the minions of the hammers controller. Most of the Knights have accepted their powers and responsibility in exchange for a single wish. However the main character Yuuhi is a cynic and a pessimist who thinks that maybe destroying the world wouldn't be such a bad thing. Even more troubling is that the Princess Asahina Samidere only wants to protect the earth so that she can destroy it herself. From there the story follows their efforts to fight off minions while plotting to betray their allies at the last moment.
The story flips between comedic parody of similar stories to deep character development. The premise is absolutely absurd and the characters acknowledge it regularly. Even so the story is very moving at times especially as the story progresses. The main characters are completely aware that they are actually the villains of the story and that they plan to betray all of their allies.
Overall the series is very enjoyable but flips mood fairly often and is a bit absurd at times. I would recommend this series to people who enjoyed reading shounen manga when they were younger and want to relive some of the thrill of that genre but don't want to spend months getting up to date or want a more mature storyline.