OPM is a great Shonen manga that also parodies the genre.

Despite its predictable conclusion of "Saitama will punch it," the battles actually tend to be quite intense. This is mostly because Saitama often isn't in the battles, and never really "saves," the other people involved in the battle. Saitama is often preoccupied with another fight, or is completely clueless about the battle taking place. This actually sets the stage for all the other fighters to have some nice battles where the power levels are pretty even. Along with the fantastic art, OPM actually functions as good Shonen, even if it sets out to parody it.

Like I said, it parodies the genre at the same time. Saitama is a joke on the classic Shonen hero; unstoppable, always wins, but described to be "your everyday hero, the average guy." Genos is a joke on the more edgy characters with tragic backstories that look 10x more powerful than the main hero, but in reality they aren't at all. There's another character later, "Bang," who is the stereotypical wise martial arts instructor. Several characters are non allusion jokes, like "King," or "Pri-Pri-Prisoner." Overall, a very funny manga as well, and mixes action and the comedy fantastically. It knows when to be serious, and it knows when to be a complete joke.

As a whole, OPM is incredibly enjoyable to read. You'll find several references to other Shonen stuff, and even some jokes about Western stereotypical heroes. The worst part about it is how short the chapters are, chapters that don't come out too often either. In summary, I give it a 9/10.