Best friendly fire line in your opinion

[RogerDatSoldier]

I'd say for me is from Coach that he says "Hey Nick, that was my ass you shot!"

[Willow Wife]

Yeah, Coach really has the best ones. My favourite is, "Oh hell no, boy, don't you be shootin' me!"

[England is not a real country]

The iconic...

WHAT THE HELL ARE YA DOIN` FRANCIS!

My 2 fav its nicolas one for the tank;

It´s 12 feet tall,6 feet wide...HOW ARE YOU SHOOTING ME?!

ITS THE SIZE OF A TRUCK! HOW ARE YOU MISSING?!

Perfect way to casually scream at newbie that its constally causing friendly fire accidents involving fighting against a tank;

[half]

you shoot me again and I'll knock you into next week

[Cursed Hawkins]

Originally posted by Highly Endangered Casual Medic:

"Oh hell no, boy, don't you be shootin' me!"

That's a generic one though because anyone can trigger that one, its the ones that actually name specific characters that tend to be the best ones because they are the most rare.
Edit: like just to go off of OP's quote from Coach, Francis has a similar line when Bill shoots him.
"Nice shot Bill, that was my ass"

[Johnny Casey]

"In case y'all didn't know, it hurts to get shot."
--- Ellis

[Kenn_Ethic]

"Nice shot, Bill. That was my ass!" - Francis

[umbrella15]

Nick-If you do that again, i'll bury you alive.

[England is not a real country]

Originally posted by Johnny Casey:

"In case y'all didn't know, it hurts to get shot."
--- Ellis

"No $hit,ellis..."
*Shots again*
*laughter*
"nobody wants to hear you stupid stories ellis..."

---Cut dialog from Nick
Source

[[Tяαgιιc] Rasputin]

''There is gonna be some biblical ♥♥♥♥ happening to you if you do that again!''

[Cursed Hawkins]

Originally posted by weedley_postal4.mdl:

Originally posted by Johnny Casey:

"In case y'all didn't know, it hurts to get shot."
--- Ellis

"No $hit,ellis..."
*Shots again*
*laughter*
"nobody wants to hear you stupid stories ellis..."

---Cut dialog from Nick
Source

Speaking of the cut dialog, there seems to have been a different version of Left 4 Dead as an entire genre difference because Louis has cut introduction lines for all of the L4D1 campaigns (minus Crash Course of course) that seems to imply he was going to be the only playable character at one point and the others were either side characters or background characters.
No Mercy.
[ Intro ] "I used to take the subway to Mercy Hospital. Grab the red line, a transfer, and two stops. When this gets back to normal, I'm never gonna complain about that transfer again."
Death Toll.
[ Intro ] "Me and my family used to go camping down by the lake. That's where we were heading...only, it wasn't Momma's cookin' waiting for us at the end of this trip."
Dead Air.
[ Intro ] "We were gonna take the roof tops to the airport. It was supposed to be about a mile to the terminal. Longest damn mile of my life."
Blood Harvest.
[ Intro ] "We started out on a hill top. Far as I was concerned, that's where we should've stayed. Instead, we headed to a farm house on the bad side of the tracks. Nowadays, though, I guess it's all on the bad side of the tracks."
All of these seem to give the impression that he's speaking directly to someone else that's unknown to us and the actual game is a retelling from his memorizes, there's an ungodly amount of cut dialog from the original cast, some of which that make the game seem like it was going to be a different genre as a whole during its development.
Edit: but then again, that seems to be a common trend with all of the original cast, that seem to have cut introduction lines.

[England is not a real country]

Originally posted by Cursed Hawkins:

Originally posted by weedley_postal4.mdl:

"No $hit,ellis..."
*Shots again*
*laughter*
"nobody wants to hear you stupid stories ellis..."

---Cut dialog from Nick
Source

Speaking of the cut dialog, there seems to have been a different version of Left 4 Dead as an entire genre difference because Louis has cut introduction lines for all of the L4D1 campaigns (minus Crash Course of course) that seems to imply he was going to be the only playable character at one point and the others were either side characters or background characters.
No Mercy.
[ Intro ] "I used to take the subway to Mercy Hospital. Grab the red line, a transfer, and two stops. When this gets back to normal, I'm never gonna complain about that transfer again."
Death Toll.
[ Intro ] "Me and my family used to go camping down by the lake. That's where we were heading...only, it wasn't Momma's cookin' waiting for us at the end of this trip."
Dead Air.
[ Intro ] "We were gonna take the roof tops to the airport. It was supposed to be about a mile to the terminal. Longest damn mile of my life."
Blood Harvest.
[ Intro ] "We started out on a hill top. Far as I was concerned, that's where we should've stayed. Instead, we headed to a farm house on the bad side of the tracks. Nowadays, though, I guess it's all on the bad side of the tracks."
All of these seem to give the impression that he's speaking directly to someone else that's unknown to us and the actual game is a retelling from his memorizes, there's an ungodly amount of cut dialog from the original cast, some of which that make the game seem like it was going to be a different genre as a whole during its development.
Edit: but then again, that seems to be a common trend with all of the original cast, that seem to have cut introduction lines.

Valve has this weird thing for cutting things;
they did that with rochelle,
They discard then re-make it from the ground.

[Snowman]

"Do... I... look... like one of them?!!" -Louis

[COVID-20 (No Monitor)]

Nick: "IT'S THE SIZE OF A TRUCK, HOW ARE YOU MISSING?"
Coach: "I swear to god you can't, shoot worth a ♥♥♥♥"
Francis: "You having some kind of flashback, old man?"

[Cursed Hawkins]

Originally posted by weedley_postal4.mdl:

Originally posted by Cursed Hawkins:

Speaking of the cut dialog, there seems to have been a different version of Left 4 Dead as an entire genre difference because Louis has cut introduction lines for all of the L4D1 campaigns (minus Crash Course of course) that seems to imply he was going to be the only playable character at one point and the others were either side characters or background characters.
No Mercy.
[ Intro ] "I used to take the subway to Mercy Hospital. Grab the red line, a transfer, and two stops. When this gets back to normal, I'm never gonna complain about that transfer again."
Death Toll.
[ Intro ] "Me and my family used to go camping down by the lake. That's where we were heading...only, it wasn't Momma's cookin' waiting for us at the end of this trip."
Dead Air.
[ Intro ] "We were gonna take the roof tops to the airport. It was supposed to be about a mile to the terminal. Longest damn mile of my life."
Blood Harvest.
[ Intro ] "We started out on a hill top. Far as I was concerned, that's where we should've stayed. Instead, we headed to a farm house on the bad side of the tracks. Nowadays, though, I guess it's all on the bad side of the tracks."
All of these seem to give the impression that he's speaking directly to someone else that's unknown to us and the actual game is a retelling from his memorizes, there's an ungodly amount of cut dialog from the original cast, some of which that make the game seem like it was going to be a different genre as a whole during its development.
Edit: but then again, that seems to be a common trend with all of the original cast, that seem to have cut introduction lines.

Valve has this weird thing for cutting things;
they did that with rochelle,
They discard then re-make it from the ground.

Well there's more dialog lines that got cut that hinted that the game was going to play differently, another example is Zoey calling someone by the name of Nelson but there's nobody in the entire Left 4 Dead universe that goes by that name meaning that Nelson was Francis's original name before being changed or Nelson was an NPC the group would have encountered, possibly either in Death Toll or in Dead Air (since both campaigns have a clothes shop you can go through) but that just makes you wonder how that version of the game would have played, because those lines remind me of how Splinter Cell Convictions has the entire game being told through the memorizes of what Sam told Victor.

[Senpaija]

Bill: "BE CAREFUL!"
Nick: "Well thank you for ventilating my suit."
Ellis: "I'm so mad, I could.... ♥♥♥♥ out a squealin' worm, right now!"
Coach: "Hey, Nick—that was my ass you shot."
Louis: "Go on! Do it one more time, fat man!" (Did he just call Francis fat..?)

I just collected some funny lines, they are not necessarily my favourites.