For some reason, Blizzard put in weapons completed done in a gold skin that rewards people with a bunch of competitive wins.  Like 3,000 points worth.  Just like silver and gold portraits, all that means is YOU PLAYED A LOT.  So oooh look that Widow has a golden gun.  Big deal, they just played a lot and got enough points.  It’s not an indication of skill on any particular class.

I personally haven’t done much competitive because golden “guns” doesn’t motivate me.  First off, it barely looks any different at all on some skins.  I believe Mercy in particular has a skin that already has a golden weapon.

The gold barely makes a difference on some characters, like here’s a Reaper example.

Regular weapon (Halloween skin)

Gold weapon

It barely seems worth the work to me.  Maybe if it had a Power Torrent enchant or something.