Yes, you too can weild the Scarab Gun - it takes a bit of doing, but here are the instructions

Start on the Metropolis Level
Kill the marines on the Scorpion
Cross the bridge, destroying all of the Wraiths and Ghosts, killing any marines you encounter along the way
Take out all but one Banshee at the end of the bridge - this is IMPORTANT that you leave one alive
Make sure that you grab a Ghost before entering the tunnel
Keep the Banshee following you by shooting at it every now and again, otherwise it'll "lose interest" and fly off
When you get to the first barrier, kill the marines in the Warthog, otherwise they'll take down the Banshee
Kill all Covenant resistance along the way, but keeping the Banshee following you
If the Banshee gets stuck in a corner, walk up behind it and walk backwards - this will get it to "re-target" you and follow
The stickiest point is trying to get the Banshee through the small tunnel - you might have to knock off the ends of it's wings to get it to fit
Now is the most important part of the process:
As soon as you see the "Loading... done" message, board the Banshee - if you don't, then it will vanish and you'll have to restart the whole proccess
Once in the Banshee, fly up towards the twin bridges
In the middle of the top of the first bridge is an orange cone - this contains the Scarab Gun
The Scarab Gun has unlimited ammo and never over-heats, on top of being the most powerful weapon in the game

Enjoy

Hey cool tip, thanks!

I am going to give this one ago!!

hey im new and this is awesome