This is a departure from my usual guides. This is catered to those people that want to give the illusion that they are using a gun/musket in EUO.
Warning, I have not tested this out yet so some steps may not be possible. Also your files will probably get written over during updates, so have backups.
Step 1: Make or use a rogue character, half troll is also a plus imo. Get creative with the name if you want the full illusion of a gunman/gunwoman.
Step 2: Get an avatar with empty hands that doesn't show what weapons you're holding (artful dodger/child, merchant, gremlin, wight, imp, other non-humanoid monsters, etc) or you can get one with a guitar (bard, cowboy, minotaur bard, grateful dead).
Step 3: Use a sling(s) and name it after a disguised gun (e.g. wrist mounted gun, guitar-shaped musket, etc), copper slings work well for fast firing.
Step 4 (optional): Overwrite the sling sound in your EUO sound folder with the musket sound. You will be the only one hearing it as a musket though.
Step 5 (optional): Lift one of the two musket avatars from Escape from the Vault and put it over the avatar you're using, this will only work if your avatar doesn't have a visible weapon equip like the ones I listed above. You will be the only one seeing yourself with this avatar though.
Step 6 (optional): Get a custom title like Grandmaster Gunslinger, Grandmaster Musketeer or something like. Helps a bit with the immersion.