The prize wheel.
Prize Wheels are items that can be bought at the store, found in chests, or dropped as loot. They come in three "sizes" and will give various items. The larger the prize wheel, the higher chance there is of winning an expensive item (like the Infinity Blade).
To use a prize wheel, press "use" in your inventory, then spin the wheel. If you do not spin it with enough power, you must spin it again.
Some people in the past, however, have complained that these prize wheels are fixed and that you can only win certain prizes rather than the ones displayed. Nothing on this issue has been confirmed though.
Prize Wheel
Prize Wheels cost 
7,500 and give a low chance of winning an expensive item. These prize wheels frequently appear in chests or as loot from enemies. They are red in appearance.
The player starts with 3 Prize Wheels in their starting inventory.
Big Prize Wheel
Big Prize Wheels cost 30,000 and give a medium chance of winning an expensive item. They are blue in appearance.
Rare Prize Wheel
Rare Prize Wheels cost 125,000 and give a high chance of winning an expensive item. They are yellow in appearance.
Clashmob Prize Wheel
Clashmob Prize Wheel is a new type of Prize Wheel only rewarded in certain Clashmob events. So far two have been revealed. This Prize Wheel gives the player a list of items depending on their level. It chooses one of the Clashmob prizes.
Gem Wheels
Gem Wheels are different types of Prize Wheels. They can drop Gems instead of items. There are two different types of Gem Wheels.
Ordinary Gem Wheels can be bought for 50,000 and give you new gems.
Big Gem Wheels can be bought for 700,000 and give you high end new gems (capped gems, unique weapon type gems, etc.).
Infinity Blade III
Prize Wheel: 100 chips
Big Prize Wheel: 300 chips
Rare Prize Wheel: 600 chips
Gem Wheel: 40 chips
Big Gem Wheel: 250 chips
(new) Rare Gem Wheel: 1000 chips