I saw this on Japanese tv and had to go to the source on it. There is a Kamehameha contest in which people act out the part when a Super Sajin does his Kamehameha attack from Dragon Ball Z. Here is the video of the whole contest and here is the video of the two finalist. Pretty funny. I also found some videos of people using Adobe After Effects to make it look like they are throwing fireballs. The best video I have found so far is here. Really, really, well done.