“It’s a red shower for a big fist.” She has partial hearing loss (4 years of working around mainframe computers 12 hours a day), so some syllables sound alike to her like S & F. She spent 5 years in the Army, so we can use their phonetic alphabet: sierra and foxtrot respectively.
I think her best “quote” was screaming out “mushroom!” one night when we were midget farming. If I could find a picture of a midget jumping out of a locker, I’d put it on a t-shirt. 
“That was too easy.” – Axton, after tricking his captors into deploying his turret
“I am a woman of science and ass-kickery, not children’s beverages.” (sips cocoa) “Dammit, that’s really good.” – Gaige’s ECHO Recorders
“I WIN!” – misheard 2W quote from Gaige; she actually says “I LIVE!”
“Wow, I’m already impressed.” – Jack, when Angel tells him that Axton had gotten himself captured.
“I’m back, bitches!” – Maya, attaining 2W
“This seat is sticky; why is it sticky?” – Maya, when changing seats
“Uh… it was fun?” // “Killing bad guys is always fun.” – Salvador’s response regarding killing 3 guys, much to the judge’s disbelief
Bartender: "HOLY SKAGSUCK, you decapitated Zeke! Why - why's your helmet say 'zero'?" Zer0: "He was no challenge. / My skills have not been tested. / I need something more."
For some damn reason I love the bruisers in BL2. I get a kick out of everything they say.
“Come on little one, time to die!”
“G**damn mercs!”
Love it when scooter refers to a skags mouth as a “cooch mouth”
Also when the Torgue machine says “now go punch some bad guys in the dick”
A “conversation” between Gaige and Maya:
“Was it good for you?”
“Oh I enjoyed that!”
“Ew! Ew! Ew!”
“Let’s do that again sometime!”
Lt. Col. Space Helicopters (???): http://orcz.com/Borderlands_2:_Lt_Col_Heli_Quotes
“Too bad it’ll all be gone when the Vending Machines come to life.”
“MOTHERF****** SEE YA!”
That campaign probably has the best quotes.
As I’m about to throw a grenade, nomad says “toss grenades!” Marauder replies -“Finally a good idea!”
I sometimes had situations where someone says to toss grenades while I’m about to throw them myself, but that extra line made it feel even more immersive and ironic.
easily the Spoon story where he ends it with “Hahaha idk I guess you just had to be there… Moral of the story is you are a total b****”
“Please excuse the manner of speaking which is coming out of my face mouth to say you.”
Torgue entertains me to no end.
also random gibberish from Sanct citizens like " I think I have turbo cancer " catch me off guard at times and make me lol.
(Edit) Also I’d like to mention the funny respawn quotes that get even more bizarre in the Tina Tina DLC ( if I remember right ).
things such as:
Don’t think of this as war profiteering, think of this as war… fun!
Don’t worry about the afterlife Hyperion customer. Hell is reserved
& especially the one along the lines of “if an idiot says that life is meaningless w/o death, Hyperon suggest you kill them” or something to the effect.
exclusivelt for pedophiles and people who buy Jakobs munitions
The turbo cancer quote is great.
Tannis (dp)…
“Thats not feces you smell, it’s bandits…and feces”
Mr. Torgue…
“now go make your way to the arena while I play you a sick guitar solo”
“Now go blow up the ocean!”
Random bandit(s)…
“I need a powerful woman right now!”
axton…
“You get a bullet and you get a bullet and you get a bullet…everybody gets a bullet!”
“ALAN WRITE SOME DIALOGUE HERE!!” would be my personal favorite.
But there are so many good quotes. Torgue, regular psychos and Krieg are all particularly quotable.
Jack’s spoon story: The first time I heard the part where he said “…and kids are all WAAAAHHH!!” I totally lost it. Voice acting was just too perfect there.
Here are some of my favorite BL2 quotes:
“Whatever, I don’t need ammo.” -Maya (When you run out of ammunition.)
“I want everything you got!” -Nomad
“Another one down!” and “You won’t enjoy this.”
-Maya (When she phaselocks)
“Next time you’re bleedin’ to death, Just think. Dr. Zed!” -Dr. Zed’s Vending Machines
Today I heard a woman in Sanctuary sing, “sittin’ in a chaaair!” and I laughed way more than I probably should’ve.
I love Krieg’s “stranger danger!” and “get STYLED upon!”
Claptrap’s list of weaknesses is excellent as well.
Hadn’t really noticed before today, but one of the NPCs in Sanctuary seems to channel Kreig - “I’m full of meat, and gravy!”
You also get this for the link to the Weird Al vid 
And just to stay on topic, one of my favorite bits is the line from Doc Tannis after you’re formally introduced to her: “You can only imagine in your dreams- or in my bed- standing offer!”