Nice, tiebasher, it was obviously and excalibur shell, with proximity sensors, geeez :P
Its green, low res, and uses dodgey routines to texture it. And the explosion wasnt too good.
I think that maybe you should add a multistage explosion, and make it so the piecec will bounce off the plane. And also make sure that you ahve gravity on the pieces, so they fall back down to earth.
I would tell you to add some flames and smoke, but idk how to do that, though i have seen it done.
If you wanted a fireball you could just a liquid, make it expand, and give it acceleration upwards, and the consistency of oil, so it would be a nice rolling fireball from the explosion. Maybe you could use vertex array sor something to make it go explode.
All in all, nice but basic, needs work
EDIT: ninjaed that shotgun up :P
Looks nice, but again its lwo poly and textures need work