The basic premise of the game is you somehow kill the 11th best assassin in the world and as such you decide it would be a great idea to work your way through the ranks to become numero uno. Between killing the top 10 assassins you have to collect enough cash to apply for these battles in an open (but not too open) world-style city called Santa Destroy. That's pretty much it.
While the game is far from perfect (holy shit is it ever), the basic charm of it is that it knows it's a video game. It uses a lot of very old school sound effects (mainly for menus and such) and important map areas are marked by strange pixel-y markers representing whatever the spot is (a gym, a bar, employment office, assassin-for-hire place and so on).
I'll be honest in this brief review and say that the open world aspect is not overly impressive, nor is it very compelling. Many games have done it a lot better (though Santa Destroy is a small town, unlike the city in Crackdown or something, so it at least isn't attempting to be overly ambitions and failing horribly) and at times the complete lack of anything resembling physics will make you laugh (for example hitting a car causes you to stop, once in a while falling off your bike, but many other times you just stop and bounce off it).
However where the game really shines is the combat. Rather than opt for endless Wii remote swinging, the developers went with a much simpler control scheme of hit 'A' to swing your sword, and hit 'B' to kick or punch. Coupled with aiming your remote low or high (determined by the tilt) for low and high attacks, the control scheme is amazingly effective and very comfortable. There is a minor amount of swinging; when you take an enemy's health down to zero you are given a finishing move, done with a quick flick of the remote either vertically or horizontally. This ends with cutting a dude's head off (or slicing him down the middle) followed by an excessive amount of both blood and coins.
Combat against standard enemies is repetitive and not overly challenging, but somehow manages to never stop being fun. The game's bosses are where your combat skills are really put to the test. Each boss gets progressively harder and teaches you new levels of patience (most will dodge all your attacks if you go after them without regret, and then quickly take a huge chunk of health) as you wait for them to lower their guard (normally done when they are taunting you or miss a big attack). Each one is also surprisingly unique, and range from a sword wielding schoolgirl, to an anti-Superman, to army chick with a fake leg.
The story and writing of the game is entertaining, though faulty and downright bad at times, though the fact that the game's style and combat are the main focus make it okay by me. The story takes various strange turns that often seem like they are going nowhere, or certain aspects will pop up and make you go "wait, what?" almost seeming as if they were made up on the spot. Still, you can hardly fault a game with crazy lighting and a spiky haired anti-hero wielding a modified light saber katana as the main protagonist.
No More Heros is just one of those games that's pure fun, and ends up being highly enjoyable thanks to just believing it's an old video game. Hilariously crazy storyline coupled with killing a fuckton of guys and a protagonist of morally questionable views. What could possibly go wrong?