The Boxing Toy is the first weapon you will obtain (you have to buy this). It Swings about 4 times in a second. A fully upgraded Boxing Toy will give you 2-3 coins per hit. An orange-coloured ring will appear once the glove hits the boss. After some swings, the boxing toy will send out a big punch that will stun the boss and move him to another part of the room.
The Boxing Toy itself costs 500 coins, and the upgrade costs 750 coins.