BFG. Most of the gamers know the BFG from Quake II. According to Wikipedia  the first game where we found this weapon.

Later, Doom has copied it, what better compliment can you get? Even in the film Doom, where at one time, The Rock gets his hands on a BFG9000, only they call it a "Bio-Force Gun".

The BFG looks like a canon, and is a two-hands weapon. When you jerk the trigger, it takes a couple of seconds to power-up, then it launches a green plasma ball which travels relatively slow through the level. The plasma ball shoots green laser beams to surrounding enemies. If the ball makes kontakt, it explodes with enormous strength.

For my casemod, I will be using the shuttle PC, because of its size. The PC casing will ga away and I will build a sortof canon-barrel around it. The length of the case will be 1 meter, any longer would not be "controlable" :)
On the front of the Shuttle chassis, I will mount a little motor (like in the left arm of The machine casemod) and I will let it run at around 1.5 volts. On the axel of the motor, I will mount a large green-radiant ball. I'll paint the ball with Glow-in-the-Dark powder what I have left from the last casemod.
 

Around the ball I will mount UV CCl lights and behind the ball a small stroboscope light. Maybe I can manufacter a trigger mechanism somewhere which I would like to connect to that stroboscope. Should look nice :)

The barrel will have no windows, or just a small one for the videocard. I rather would like to make gills or airscope's.
I have several small sub-projects in my mind for the case, but i'll come back to those later on. When the barrel outershell will be finished technically speaking, i'll be painting the thing with camouflage colours, black, brown and green.
How and what I will do with all the cabels, i'm not sure yet. Maybe all cables in one large flexcable tube.

You can check out my progress on any of these forums where I post the latest worklogs.