This guy is the funniest writer alive, and since no-one's put a fatwa on him yet, this state of affairs is likely to continue for some time. Some of the best quotes are here, from just five of his books. I have modified some of them to prevent them from being context-specific.
Maskerade
Her attitude to music was purely ballistic - just point your voice at the end of the verse and go for it.
he'd twice failed to become Village Idiot through being overqualified.
Her forehead wrinkled, as it tended to whenever she considered a question more complex than "What's your name?"
There was a crash from the direction of the kitchen, although it was more of a crescendo - the long-drawn-out clatter that begins when a pile of plates begins to slip, continues when someone tries to grab at them, develops a desperate counter-theme when the person realizes they don't have three hands, and ends with the roinroinroin of the one miraculously intact plate spinning round and round on the floor.
"They said we should mount guards and they'd take steps."
"To the nearest place of safety, no doubt."
It's easy to hold everything in common when no-one's got anything.
He counted to one on his fingers. Then he counted to two.
"We're witches and we will pay our way by curing you of any irritating ailments you have."
"I don't have any."
"How many would you like?"
Hogfather
He was considered by Ankh-Morpork's professional underclass to be something of an intellectual because some of his tattoos were spelt right.
The Quirmian philosopher Ventre put forward the suggestion that "Possibly the gods exist, and possibly they do not. So why not believe in them in any case? If it's all true you'll go to a lovely place when you die, and if it isn't then you've lost nothing, right?" When he died he woke up in a circle of gods holding nasty-looking sticks and one of them said "We're going to show you what we think of Mr Clever Dick in these parts..."
To him breathing was an intellectual that had to be concentrated on. He could just manage one nostril at a time at the moment.
Cats that had mastered every detail of feline existence except the location of the dirtbox.
That statement is either so deep that it would take a lifetime to fully comprehend, or it is a load of absolute tosh.
Drinks like this tend to get called Traffic Lights or Rainbow's Revenge or, in places where truth is more highly valued, Hello and Goodbye Mr Brain Cell.
"Divide by cucumber error. Please reinstall universe and reboot."
"What do you call that warm feeling you get inside?"
"Heartburn?"
"I could certainly run a marvellous university here if only we didn't have to have all these damn students underfoot all the time."
"I am sure he wouldn't keep eating them if they were addictive."
"I really should talk to him. He's had a near-death experience!"
"We all have. It's called living."
Equal rites
...although his body had been around quite a lot his mind had never gone further than the inside of his head.
He had that kind of real deep tan that rich people spend ages trying to achieve with expensive holidays and bits of tinfoil, when all you really need to do to obtain one is work your arse off in the open every day.
Granny knew all about bad fortune telling. It was harder than the real thing. You needed a good imagination.
"That new lad. You know, the one they say has got a whole head full of brains?"
They both savoured the strange warm glow of being much more ignorant than ordinary people, who were ignorant of only ordinary things.
Cutangle stood with legs planted wide apart, arms akimbo and stomach giving an expression of a beginners' ski slope, the whole of him therefore adopting a pose usually associated with Henry VIII but with an option on Henry IX and X as well.
Reaper Man
"It's not that I don't want (to die)...it's just that life is a habit that's hard to break."
While wizards don't believe in gods they know for a fact that gods believe in gods.
In the distance a couple were having the kind of quarrel that causes most of the surrounding streets to open their windows and listen in and make notes.
Ankh-Morpork has always had a fine tradition of welcoming people of all races, colours and shapes, if they have money to spend and a return ticket.
"It's called a shovel... I've seen gardeners use them. You stick the sharp end in the ground. Then it gets a bit technical.
autocondimentor - someone who will put salt and probably pepper on any mean you put in front of them regardless of how much it's got already and regardless of how it tastes.
The patrician (tax-collector) said...it was two hundred dollars per capita; if per capita was a problem, decapita could be arranged.
"She's a (spirit) medium. Well, more a small."
"Why does everyone run towards a blood-curdling scream?...It's contrary to all sense."
"We'll strategically withdraw to previously prepared position."
"Who prepared them?"
"we'll prepare them when we get there..."
"Have you any last words?"
"Yes. I dont want to go."
"Why are you called One-man-bucket?"
"...In my tribe we're traditionally named after the first thing my mother sees when she looks out of the tepee after the birth. It's short for one-man-pouring-a-bucket-of-water-over-two-dogs."
"That's pretty unfortunate."
"It's not too bad. It was my twin brother you had to feel sorry for. She looked out ten seconds before me to give him his name."
"don't tell me, let me guess. Two-dogs-fighting?"
"Two-dogs-fighting? Two-dogs-fighting? Wow, he would have given his right arm to be called Two-dogs-fighting."
Sourcery
...the complete carcass of a whole roast pig looked extremely aanoyed at the fact that someone had killed it without waiting for it to finish its apple...
One of Rincewind's tutors said that 'to call his understanding of magical theory absymal is to leave no suitable world to describe his grasp of its practice.'
No wizard would normally dream of giving a colleague a leg up unless it was in order to catch them on the hop.
They looked at each other with mutual. grudging admiration and unlimited mistrust, but at least it was a mistrust each of them felt he could rely on.
"Quick, you must come with me, you're in great danger!"
"Why?"
"Because I'll kill you if you dont."
"my mother ran away before I was born".
He looked sideways into the leering faces of men who would kill him sooner than think , and in fact would find it a lot easier.
"Why me?"
"For the good of the university. For the honour of wizardry. For the sake of the world. For your heart's desire. And I'll freeze you alive if you don't."
Rincewind breathed a sigh almost of relief. He wasnt good on bribes, or cajolery, or appeals to his better nature. But threats, now threats were familiar. He knew where he was with threats.
"What did it feel like?"
"Have you ever been bitten by a viper?"
"No."
"In that case you'll understand exactly what it felt like."
"hmmmm?"
"It wasnt like a snake bite at all."
"I cant swim."
"Not a stroke?"
"About how deep is the sea here, would you say?"
"About a dozen fathoms I believe."
"Then I could probably swim about a dozen fathoms, whatever they are."
River water is incredibly pure - anything that has passed through so many kidneys must be.
"Today the city, tomorrow the world."
"Tomorrow the world, and - " he calculated quickly, "on Friday the universe! Good, that leaves the weekend free..."
The shape of DNA, it is popularly said, owes its discovery to the chance sight of a spiral staircase when the scientist's mind was just at the right receptive temperature. Had he used the lift, the whole science of genetics might have been a good deal different. Although, possibly, quicker. And only licensed to carry fourteen people.
He was staring fixedly at his finger, holding it out at arm's length in a manner that suggested he was very sorry he hadnt got longer arms.
...stones that were missing him by inches and in some cases, hitting him by kilograms.
...where his fall was broken by the floor.
It wasnt lost. It always knew exactly where it was. It was always HERE. It was just that everything else seemed to have been temporarily mislaid.
"Now hold on a minute."
They held on a minute.
They held on a further seventeen seconds.
Rincewind's mind was operating at the speed of continental drift.