Garry's Mod

Can someone give me some tips on how to make some cool shots like all the admins and members have in their sigs and avatars? Heh, the very best I can do is make a pile of dead bodies, but even that looks lame. Also, I was wondering how you make the muzzle flashes, the explosions, and the tracer rounds. Do you do it in photoshop or is there like a special way to do it?
The tracers can be made using the "Turret" STOOL.

As far as muzzle flashes go, shoot for the "Emitter" STOOL.