This is where all equipment,weapons, and armor are bought. There are two vertical menus, one on either side of the Slot Machine. The menu on the left deals with weapons while the menu on the right includes Attachments and Armor.
The items available in the shop menus change whenever a game is completed. When an item is bought, it vanishes from the shop and appears in the equip menu. The empty space in the shop remains empty until a game is completed. Some items appear in the shop a lot (for example the PDW) while others, Flawless items in particular, are a more rare occurrence.
If you spot a rare item in the shop, but don't have enough money to but it, the item may vanish by the time you have the funds. A good way around this is to play a match without finishing it, for example a first-to-50 Death Match which you quit on accumulating 45 kills.
Don't forget, you get XP during matches to level up. Funds are XP x4. So, for every 1 XP, you get 4 funds! In match, you can see your XP and money at the bottom of the game screen. This can be useful if you are only playing to get a certain amount of funds, like in the above situation.
In SFH 2, money is more a tool for experimentation, so you can afford to test out most weapons. A bigger restriction is the space in your inventory!
The Slot Machine is postioned in the middle of the Shop screen. Playing it results in a higher chance of "special" weapons, but also of "useless" equipment. You can also win better armor and equipment. However, the price is gradually increased until the class is maxed, (level 50) to $3000 a spin. There are 7 different symbols in the slot machine.
'Poop': Getting 3 in a row of this will give you a worthless item that cannot be taken or equipped, only sold or left. However, there is a chance to get two extremely unique and powerful weapons, the Dooty Launcher and the Sheep Cannon.
Shield: Getting 3 in a row of this will give you an armor piece of random quality, usually normal, refined, or occasionally flawless.
Money symbol: Getting 3 in a row of this will give you an amount of cash equivalent to 1.5x the spin fee.
Crosshairs: Getting 3 in a row of this will give you a random weapon attachment of any quality.
Revolver: Getting 3 in a row of this will give you a random weapon; the chances of getting a particular quality are more or less identical to the shop's.
Star: Getting 3 in a row of this will usually give a refined random item, although it is possible to obtain a flawless item as well. On very rare occasions, you may get a perfect item.
Nine: Getting 3 in a row of this will give you a flawless, refined, or perfect weapon, with a heavy pitch towards flawless. You can also get an attachment or an armor.
SFH2 Symbol: Getting 3 in a row of this will give you a sum of money (2x of the fee to spin) and a perfect weapon. This is also called a jackpot, and it will give you an achievement on Armor Games.
'Camo': Getting 3 in a row of this will unlock the next camo of this class. (When you unlock all the camos for a soldier, you cannot get 3 'Camo' in a row any more.)