I'm fairly certain that this may have been
covered before... so I'll just get right to the point:
I heard, read, that you could have three
weapons in legendary if you'd finished the game in normal mode.
so I set about doing so.. and did.. and tried to see if it was true.
and although it seemed a lot more like a
bug than a feature.. it sure was true.. here's how:
first, as I said.. finish it on normal.
then, while playing on legendary, in the pillar of autumn.. run as darned
fast as you can do the bridge.. jump over the guy that tells you to follow
him.. then skip the sequence.. and run away from the captain..
if you were as lucky as I.. you'll see
that you in fact, don't have your gun with you after you've ran out... and
the small little grunts wont be there waiting for you either.
pick up the AR.. and use it to get a Plasma rifle.
then go back to the captain... say hi.. or
slap him.. or whatever..
then go back out again.. for some reason, you'll now get the pistol.
voila.. you'll now have a Plasma Rifle, an
Assault Rifle and the Pistol.
some of these things may not be necessary
to do. but it's what I did when I discovered this.
also.. I've only seen it work on pillar of
autumn... I tried it on 'halo' and SC as well.. but it didn't work there.