This effect can overlay patterned sparks to any Final Cut Pro X clip:
Here are the controls:
You have the choice of three different particle shapes, and can animate the location, size, number of sparks, speed and the strength of gravity acting on the sparks.
If you have Motion installed, or you have already installed third-party effects, download the effect archive from here.
Expand the ZIP archive and add the folder to Movies : Motion Templates : Effects : Alex4D :
If you don’t have Motion installed on your Mac and you’ve never installed any third-party effects, download the archive of the Motion Templates folder with the Sparks effect in the correct sub-folder. Expand the ZIP and put the resulting Motion Templates folder in the Movies folder of your home folder.
If you find this free plugin useful, you might like my Alex4D Animation Transitions plugin pack:
There are many more free plugins on my Final Cut Pro X page