Tournaments are quite popular at online casinos and poker sites. Playing free tournaments gives you the opportunity to win big prizes. And some tournaments require you to deposit a small amount of money in order to continue playing and compete for the championship. The Grand Slam of Slots II is Microgaming's biggest slot machine tournament and takes place on the famous Thunderstruck II slot machine. The first place winner will be able to take home a huge $100,000 win.