An entertaining twist on a classic genre.
The shopping system is very generic, but fits well with the game. When you earn xplodium, you must exchange it for currency. you start the game with only one chamber in which to do this, but you can purchase additional chambers that require more waiting, but net more reward. you can then spend your money on upgraded equipment. Of course, being an iPhone game, you have an additional form of currency you can purchase using microtransactions, enabling you to buy the more elite gear.
This shooter also has humorous aspects. Every weapon and armor set has its own description, and these descriptions are witty and comical. They either describe the equipment's origin in a ridiculous fashion, or they describe the workings of the equipment in a way that sounds technical, but truly makes no sense. During load times, you also see descriptions of the various T.O.O.L. classes, which are equally entertaining to read. These descriptions add a light-hearted aura to the action.
The gameplay is simple: you have two movement pads, one controlling your movement, the other controlling the direction your weapon fires. you avoid being hit by enemies using the movement pad while shooting enemies using the aiming pad. There is no ammo or reloading involved, you only need to point, and your character shoots. the other bro will follow you around and shoot enemies as well.
Gun Bros even has a social aspect. you can use your friends on game center with Gun bros to upgrade the other bro, since otherwise he only uses the default weapon and armor. Your bro will use the equipment your game center friend has equipped, making him a much more useful partner.
Gun Bros is not without a few problems, however. Because this is a touch-screen application, your fingers will sometimes get in the way of your vision, causing enemies to appear to have come from nowhere and start damaging you. Also, despite there always being two bros at once, there is no support for online co-op or peer-to-peer gameplay. This is a major problem, because the AI for your bro is very poor. He will not shoot at enemies off-screen; in fact, he will only shoot at enemies very close to him.
All in all, Gun Bros is a very entertaining and addictive game. It is well worth both the price (free) and the space on your iPhone; you will play it again and again. This game is well worthy of being expanded and sold on XBL Marketplace or PSN, and I would not be surprised to find this game there in the future. However, if I had to describe Gun Bros in just three words, there is no debate as to what they would be: just plain fun.