OK, here's the effect you've all been waiting for!  (Or something similarly overdramatic)
By Sjet vs. Kerrigan
With beam texture and bits of code from Cnl Pepper
And Excalibur Mesh by Lt. Jim

This comes with an Excalibur, logical enough, since you wouldn't put this weapon on anything else.  It's only got the Main Gun, which doesn't shut the ship down for a minute, but oh well.  The damage on the beam is pushed to such an insane level that most ships should go down in one shot.
To make the weapon work:
Unzip this into your homeworld directory.  r1 and etg should come out in the right places.
If you don't have a weapons mod installed:
 move r1.script from the homeworld directory into the etg directory.  

If you do have a weapons mod:
Look at the r1.script that came with this file (in your homeworld directory), and copy the smallIonCannon fireEvents and BulletEffects into your r1.script.  You can then delete our r1.script, since it's not doing you any good.  Make sure none of your other ships are using smallIonCannons.