Fire Swing is Mario's Star Swing in Mario Super Sluggers. In this swing, Mario swings his bat back and forth until the end catches fire. Then, he hits the ball, sending it flying across the field cloaked in fire. If a fielder tries to catch it, that fielder will be momentarily burned. The ball will continue, but the fire will wear off after a few seconds and the ball will roll to a stop.
This Star Swing is usually effective when it comes to making runs, but if two fielders are close to each other, one will get burned, while the other can freely catch the ball, getting Mario out as a result. Additionally, if the ball is surrounded by flames and collides with an object, such as a Freezie, the flames will be put out, allowing fielders to safely catch the ball and get Mario out.