How I christened my weapon (and ended a boss fight in a single turn)

So, last night was probably the best DnD session of my life and it's a story I just had to share with you all. Unfortunately it's gonna be a bit of a long one so I'll try and include a tl;dr at the end.

First things first I should mention that this is a HEAVILY homebrewed campaign. No magic, post-apoc setting using a fairly modified 5e system. My character, Ike, was a Tinkerer. The class revolves around using scrap and salvage to modify and create weapons, ammunition and explosives. The character started with two revolvers, one of which, due to being Level 3 was assumed to have two small modifications, a sight and a suppressor. The second was immediately cannibalised into a barrel, grip, firing mechanism and revolving chamber.

Almost immediately after the party assembled we came across a collapsed caravan. Not a lot to be found except a junk shotgun. Saw it off, now Ike has a stock. So, Ike used the spare revolver barrel to extend his own and then attached the shotgun stock. Ike's weapon of choice is now a silenced revolver-rifle-thing. Despite being unable to think of a fitting name for his creation, Ike is happy.

We kill some bandits, make our way to an abandoned metropolis and fall under sniper fire. Party member injured, scour nearby building for cover/safety and medical supplied. Kill a few clickers (for the sake of enemy diversity the setting borrows a fair few enemies from various post apoc universes) and Ike obtains a break action shotgun, some c4 and some thermite. Ike is VERY happy.

So, I ask about cutting the shotgun down and mounting it to the underside of the rifle as an underslung shotgun. I even drew out how I envisioned the loading working with the break action mechanism. DM looked on in horror, but agreed assuming I could find the necessary parts.

We carry on our way and end up in an underground tunnel system. Some bandits have set up a barricade and are asking an extortionate toll for our level. Combined we don't even have enough currency to get through. Not that it matters because Ike is sneaky beaky-ing his way through a train car. We learn that these people are allied with Sergei, the sniper who had been giving us grief. Fighting happens. The suppressor and darkness keep Ike hidden and after taking down the mini boss Ike has enough experience to level up. Upon leveling up the Tinkerer gets an uncommon weapon modification. Ike now has an underslung shotgun and, despite still being unable to think of a name, is grinning from ear to ear.

Now. The boss fight. We start climbing the building our sniper friend was using. He's been harassing us since we got in the city and we have a bone to pick.

The encounter was set up by the DM to be highly tactical. The sniper had crazy high dex, so high bonus to hit and damage, but (we eventually figure out) low AC and health. He was on the roof above us, with holes in the ceiling from the building still being under construction. The encounter started with Ike lobbing an improvised explosive through one of these holes, and continued for a few rounds without anyone seeing or shooting anything.

We figured out that the half constructed ceiling was built in islands, with planks between them. Every so often Sergei would dash from island to island. So, we figured that our best chance was to destroy the planks and pin him down. Not a bad idea. We destroy two planks between us in the next round, still no shots fired or direct sightings of an enemy.

Sergei's turn, he pops out of cover and fires at Ike, it hits and Ike takes his first hit of the game. Ike's turn.

"Wait if he shot me that means I can see him right?"

"He's in half cover but yes."

"I ignore half cover. In fact I'm going to take a shot and use my sharpshooter."

I roll, 13, with the minus five from sharpshooter that comes to 15 total. I've used up all my luck points. I've gotta take it.

Roll damage, a d8. 8. Plus 3 from dex and plus 10 from sharpshooter. 21.

"How do you wanna do this?"

After taking a shot to the shoulder, Ike spun round, taking aim with his bastardisation of a revolver. As he brought the gun round his off hand curled into a raised middle finger, flipping Sergei off as he fired that one shot. The one bullet that would start and end the fight with out first real boss.

Sergei the sniper, who according to the tunnel raiders had killed hundreds of passers by, was dead with a single bullet. His reign of terror over.

Ike climbed to the roof, stripping the sniper rifle for parts. His revolver now sporting a bipod and telescopic sight. He also took Sergei's hat for good measure, ignoring the bullet hole in the back of it.

Ike's bastard weapon was finished. He had created his masterpiece. And what's more this monstrosity, this ugly old pistol that had been transformed into disgusting mess of engineering had a name.

Sergei's Bad Day.

TL;DR - Character has revolver. Customises it to a stupid degree, scopes, silencer, stock, underslung shotgun. Spent all session trying to name it. Killed the final boss, who had been harassing us for most of the session, with a single attack. Named the weapon in his honour.