Code:
function lazerAspezial()
{
   // ...
   // I know it's p.gravity = 0 and p.flags = BRIGHT | MOVE now, but I'll use the original for clarity.
   my.alpha = 21.738 ;
   my.gravity = 0 ;
   my.streak = off;
   my.flare = off;
   my.bright = on;
   my.beam = off;
   my.move = on;
   // ...
}

I think the "almost invisible" part comes from this line: my.alpha = 21.738;.
EasyParticle may fool you into thinking that looks good, but 22% is not very visible.

Also, you say it "doesn't act as a laser"... from what I understand, this effect shoots sort of a ball of energy at a random speed along the x-axis. There are a few problems with this. Number one, the laser can't be aimed at all. If you're making a side-scroller where a player can only shoot along the x-axis, this won't be a problem, but it seems like you're making a first person shooter. And number two, if you don't make enough particles (right now you're only making a max of one per frame) the balls of energy won't be numerous enough to fuse into a beam. Making more particles could also fix the "invisible" problem.

Good luck!