Do what Mardian suggested, but, DONT USE A BEAM. They are easily visible if they go over stuff, ect..
Perhaps, make these two enemy govts, give them a simi-fast weapon, but not lightning fast, and must be an invisible, unlimited fuel, smart homing thing with no sound.
Then, have them both be in/jump into the system. Both fire their shots, both blow up, ideally at almost the same second. Otherwise, there will always be something in there.
Or, you could have it be a trader Pers that is in system x 100% of the time, and that hates specialGovtB. This freighter with warship AI attacks whenever this thing comes in, ect..
I'm getting lost, oh well.
Also, for other snazzy effects, give the weapon a large impact but no radius, and small explosion. Also make sure it goes over astroids. That way, if someone watches the ship get blown up, it'll have a small explosion on one side, then go flying away, blowing up rather quickly.
~S~
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"All power corrupts, absolute power..."
"..is even more fun!"
"The meek shall inherit..."
"...what they're bloody well given. And be thankful for it."
-BOFH, Simon talking to his PFY.