A short game, but fun nonetheless.
Gun uses a mission based system, which works very well. Although there are few story missions (most of which are very interesting), the side missions make up for it. There are a few different types of side missions including Texas hold'em poker, bounty hunting, delivery missions and more. These missions are required for 100% completion. Each of the side missions are variations of a certain theme, making no two missions exactly the same. In one bounty hunting mission, you must bring someone back dead, in others you get a choice to bring them back dead or alive. Some have single enemies, whereas others have groups of enemies. This variation applies to all the side missions, apart from poker. The story mode can be completed in around five to six hours if you just ignore all the side missions, but you probably wouldn't do that. Completing side missions increases your stats, making your character faster, more accurate and a better warrior in general. There are various weapons in the game, such as shotguns, bows, pistols and more. Items can be bought with the money earned from side missions to upgrade the power and accuracy of some of these weapons. A pick-axe and a scalping knife can be bought to allow you to mine gold for extra money, and to scalp enemies for no reason whatsoever.
The world is gun is fairly large, filled with canyons and vast landscapes. The graphics are a nicely done, although they are not amazing. You can choose two means of travel in Gun: On foot or horseback. Most of your travelling will take place on horseback, as getting from place to place on foot would be quite time consuming. Riding a horse has never been so accurately modelled. The horse runs, jumps and tramples things perfectly. You can also use weapons while riding a horse, but the trample attack the horse does is devastating to almost everything.
The soundtrack for gun sets the theme well. It has stereotypical western tunes which add to the atmosphere of the game. The sound effects are done well too, although they can get fairly repetetive. Gun has some of the best voice acting and cut-scenes I have ever seen in a game.
To sum up everything, Gun is a great game. Very short but fun to play, and the side missions will make up for the short story mode. I don't see much replay value, so renting would probably be better than buying this game. Although if you like a challenge, you could try to complete Gun on the hardest difficulty, which is extremely difficult.