The fruit machine is free, and you can get good things from it. There's no skill involved; you just press a button. So, it's a good "game" to play as often as you can. The catch is that you can only play once a day. The fruit machine can be found here
Most often, you probably won't get anything, but if the right combinations come up, you can win lots of neopoints, toys and other items like food or even petpets. One time I got a Tenna and 2,500 neopoints. What have you won? You can also win paintbrushes and muffins.